Lakhmir Singh solutions for Physics (Science) [English] Class 10 chapter 2 - Magnetic Effects of Electric Current [Latest edition]

Write any three properties of magnetic lines of force.

What are the two ways in which you can trace the magnetic field pattern of a bar magnet?

You are given the magnetic field pattern of a magnet. How will you find out from it where the magnetic field is the strongest?

State whether the following statement is true of false:
The axis of earth's imaginary magnet and the geographical axis coincide with each other.

Why does a compass needle get deflected when brought near a bar magnet?

Where do the manufactures use a magnetic strip in the refrigerator? Why is this magnetic strip used?

Fill in the following blank with suitable words: 

 Magnetic field lines leave the .......... pole of a bar magnet and enter at its .......... pole.

Fill in the following blank with suitable words: 

The earth's magnetic field is rather like that of a .......... magnet with its .......... pole in the northern hemisphere.

Draw a diagram to show the magnetic field lines around a bar magnet.

What is a magnetic field? How can the direction of magnetic field lines at a place be determined?

Explain why, two magnetic field lines of not intersect each other.

When an electric current is passed through any wire, a magnetic field is produced around it. Then why an electric iron connecting cable does not attract nearby iron objects when electric  current switched on through it?

Define magnetic field lines. Describe an activity to draw a magnetic field line outside a bar magnet from one pole to another pole.        

Explain why, a freely suspended magnet always points in the north-south direction.

A strong bar magnet is placed vertically above a horizontal wooden board. The magnetic lines of force will be:

(a) only in horizontal plane around the magnet
(b) only in vertical plane around the magnet
(c) in horizontal as well as in vertical planes around the magnet
(d) in all the planes around the magnet   

The magnetic field lines produced by a bar magnet:

(a) originate from the south pole and end at its north pole
(b) originate from the north pole and end at its east pole
(c) originate from the north pole and end at its south pole
(d) originate from the south pole and end at its west pole

Which of the following is not attracted by a magnet:

The magnetic field lines:

(a) intersect at right angles to one another
(b) interest at an angle 45° to each another
(c) do not cross one another
(d) cross at an angle of 60° to one anotherv

The shape of the earth's magnetic field resembles that of an imaginary:

(a) U-shaped magnet
(b) Straight conductor carrying current
(c) Current-carrying circular coil
(d) Bar magnet

A magnet attracts:

A plotting compass is placed near the south pole of a bar magnet. The pointer of plotting compass will:

The metallic pointer of a plotting compass gets deflected only when it is placed near a bar magnet because the pointer has:

Which of the following statements is incorrect regarding magnetic field lines?
(a) The direction of magnetic field at a point is taken to be the direction in which the north pole a magnetic compass needle points.
(b) Magnetic field lines are closed curves.
(c) If magnetic field lines are parallel and equidistant, they represent zero field strength.
(d) Relative strength of magnetic field is shown by the degree of closeness of the field lines.

Copy the figure below which shows a plotting compass and a magnet. Label the N pole of the magnet and draw field line on which the compass lines 

The diagram shows a bar magnet surrounded by four plotting compasses. Copy the diagram and mark in it the direction of he compass needle for each of the cases B, C, and D. 

Which is the north pole, X or Y?

The three diagrams in the following figure show the lines of force (field lines) between the poles of two magnets. Identify the poles A, B, C, D, E and F. 

The figure given below shows the magnetic field between two magnets: 

Copy the diagram and label theother poles of the magnets.

Which effect of current can be utilised in detecting a current carrying wire concealed in a wall? 

What concealed do you get from the observation that a current-carrying wire deflects a compass needle placed near it?

Name the scientist who discovered the magnetic effect of current.

Name the rule for finding the direction of magnetic field produced by a straight current-carrying conductor.

State the form of magnetic field lines around a straight current-carrying conductor.

What is the other name of Maxwell's right-hand thumb rule?

State whether the following statement is true or false:
The magnetic field inside a long circular coil carrying current well be parallel straight lines.

What is the shape of a current-carrying conductor whose magnetic field pattern resembles that of a bar magnet?

State three ways in which the strength of an electromagnet can be increased.

Fill in the following blank with suitable words: 

The lines of ........... round a straight current-carrying conductor are in the shape of ...........

Fill in the following blank with suitable words: 

For a current-carrying solenoid, the magnetic field is like that of a ...........

Fill in the following blank with suitable words: 

The magnetic effect of a coil can be increased by increasing the number of ........... increasing the ........... or inserting an ........... core.

Fill in the following blank with suitable words:

 If a coil is viewed from one end and the current flows in an anticlockwise direction, then this end is a ........... pole.

Fill in the following blank with suitable words: 

 If a coil is viewed from one end, and the current flows in a clockwise direction, then this end is a ........... pole.

Describe how you will locate a current-carrying wire concealed in a wall.

Describe some experiment to show that the magnetic field is associated with an electric current. 

Draw a sketch to show the magnetic lines of force due to a current-carrying straight conductor.

Name and state the rule to determine the direction of magnetic field around a straight current-carrying conductor.

State and explain Maxwell's right-hand thumb rule.

What is Maxwell's corkscrew rule? For what purpose is if used?

Draw the magnetic lines of force due to a circular wire carrying current. 

 What are the various ways in which the strength of magnetic field produced by a current-carrying circular coil can be increased?

State and explain the Clock face rule for determining the polarities of a circular wire carrying current.

Name any two factors on which the strength of magnetic field produced by a current-carrying solenoid depends. How does it depend on these factors?

 Draw a circuit diagram to show how a soft iron piece can be transformed into an electromagnet.

Describe how an electromagnet could be used to separate copper from iron in a scrap yard.

 How does an electromagnet differ forma permanent magnet?  

 Name two devices in which electromagnets are used and two devices where permanent magnets are used.

What is a solenoid? Draw a sketch to show the magnetic field pattern produced by a current-carrying solenoid.

Name the type of magnet with which the magnetic field pattern of a current-carrying solenoid resembles

What is the shape of field lines inside a current-carrying solenoid? What does the pattern of field lines inside a current-carrying solenoid indicate?

 List three ways in which the magnetic field strength of a current-carrying solenoid can be increased?

What type of core should be put inside a current-carrying solenoid to make an electromagnet?

What is an electromagnet? Describe the construction and working of an electromagnet with the help of a labelled diagram.

 Explain why, an electromagnet is called a temporary magnet.

 Explain why, the core of an electromagnet should be of soft iron and not of steel. 

 State the factors on which the strength of an electromagnet depends. How does it depend on these factors?

Write some of the important uses of electromagnets. 

An electron beam enters a magnetic field at right angles to it as shown in the Figure. 

The direction of force acting on the electron beam will be:

 to the left
 to the right
 into the page
 out of the page
  

The strength of the magnetic field between the poles of an electromagnet would be unchanged if:

The diagram given below represents magnetic field caused by a current-carrying conductor which is: 

(a) a long straight wire
(b) a circular coil
(c) a solenoid
(d) a short straight wire 

Which of the following correctly describes the magnetic field near a long straight wire?

The north-south polarities of an electromagnet can be found easily by using:

(a) Fleming's right-hand rule
(b) Fleming's left-hand rule
(c) Clock face rule
(d) Left-hand thumb rule

The direction of current in the coil at one end of an electromagnet is clockwise. This end of the electromagnet will be:

(a) north pole
(b) east pole
(c) south pole
(d) west pole

If the direction of electric current in a solenoid when viewed from a particular end is anticlockwise, then this end of solenoid will be:

(a) west pole
(b) south pole
(c) north pole
(d) east pole

The most suitable material for making the core of an electromagnet is:

(a) soft iron
(b) brass
(c) aluminium
(d) steel

The magnetic effect of current was discovered by:

(a) Maxwell
(b) Fleming
(c) Oersted
(d) Faraday

A soft iron bar is inserted inside a current-carrying solenoid. The magnetic field inside the solenoid:

(a) will decrease
(b) will increase
(c) will become zero
(d) will remain the same

The magnetic field lines in the middle of the current-carrying solenoid are?

(a) circles
(b) spirals
(c) parallel to the axis of the tube
(d) perpendicular to the axis of the tube

The front face of a circular wire carrying current behaves like a north pole. The direction of current in this face of circular wire is:

(a) clockwise
(b) downwards
(c) anticlockwise
(d) upwards

The back face of a circular loop of wire is found to be south magnetic pole. The direction of current in this face of the circular loop of wire will be: 

(a) towards south
(b) clockwise
(c) anticlockwise
(d) towards north 

In the straight wire A, current is flowing in the vertically downwards direction whereas in wire B the current is flowing in the vertically upward direction. What is the direction of magnetic field:

(a) in wire A?
(b) in wire B?
Name the rule which you have used to get the answer.

The figure shows a solenoid wound on a core of soft iron. Will the end A be a N pole or S pole when the current flows in the direction shown?  

A current-carrying straight wire is held in exactly vertical position. If the current passes through this wire in the vertically upward direction, what is the direction of magnetic field produced by it? Name the rule used to find the direction of magnetic field. 

For the coil in the diagram below, when the switch is pressed:

(a) what is the polarity of end A?
(b) which way will the compass point then?    

A current flows downwards in a wire that passes vertically through a table top. Will the magnetic field lines around it go clockwise or anticlockwise when viewed from above the table?  

The direction of current flowing in the coil of an electromagnet at its two ends X and Y are as shown below:  

 What is the polarity of end X?

What is the polarity of end Y?   

Name and state the rule which you have used to determine the polarities. 

A current-carrying conductor is held in exactly vertical direction. In order to produce a clockwise magnetic field around the conductor, the current should passed in the conductor:

(a) from top towards bottom
(b) from left towards right
(c) from bottom towards top
(d) from right towards left 

A thick wire is hanging form a wooden table. An anticlockwise magnetic field is to be produced around the wire by passing current through this wire by using a battery. Which terminal of the battery should be connected to the:

(a) top end of wire?
(b) bottom end of wire?

Give reason for your choice.

What happens when a current-carrying conductor is placed in a magnetic field?

When is the force experienced by a current-carrying conductor placed in a magnetic field largest?

In a statement of Fleming's left-hand rule, what do the following represent?

(a) direction of centre finger.
(b) direction of forefinger.
(c) direction of thumb.

Name one device which works on the magnetic effect of current.

Electric motor works on the magnetic effect of electric current.

A motor converts one form of energy into another. Name the two forms.

State whether the following statement is true or false:
An electric motor converts mechanical energy into electrical energy.

For Fleming's left-hand rule, write down the three things that are 90° to each other, and next to each one write down the finger or thumb that represents it.

Name the device which is used to reverse the direction of current in the coil of a motor?

What is the other name of the split ring used in an electric motor?

Of what substance are the brushes of an electric motor made?

Of what substance is the core of the coil of an electric motor made?

In an electric motor, which of the following remains fixed and which rotates with the coil?
Commutator ; Brush 

What is the role of the spilt ring in an electric motor?

Fill in the following blank with suitable words: 

 Fleming's Rule for the motor effect uses the .......... hand.

Fill in the following blank with suitable words: 

 A motor contains a kind of switch called a .......... which reverses the current every half .......... .

 A current-carrying conductor is placed perpendicularly in a magnetic field. Name the rule which can be used to find the direction of force acting on the conductor.

State two ways to increase the force on a current-carrying conductor in a magnetic field.

 Name one device whose working depends on the force exerted on a current-carrying coil placed in a magnetic field. 

State Fleming's left-hand rule. Explain it with the help of labelled diagrams.

What is the principle of an electric motor?

Name some of the devices in which electric motor are used.

 In a d.c. motor, why must the current to the coil be reversed twice during each rotation? 

 What device reverses the current?

 State what would happen to the direction of rotation of a motor if:
 the current were reversed

 State what would happen to the direction of rotation of a motor if:  

 both current and magnetic field were reversed simultaneously. 

 State what would happen to the direction of rotation of a motor if: 

 In what ways can a motor be made more powerful? 

What is an electric motor? With the help of a labelled diagram, describe the working of a simple electric motor 

What are the special features of commercial electric motors? 

In an electric motor, the direction of current in the coil changes once in each: 
 two rotations
 one rotation
 half rotation
 one-four rotation

The force experienced by a current-carrying conductor placed in a magnetic field is the largest when the angle between the conductor and the magnetic field is: 

 45°
 60°
 90°
 180°

The force exerted on a current-carrying wire placed in a magnetic field is zero when the angle between the wire and the direction of magnetic field is: 

 45°
 60°
 90°
 180°

A current flows in a wire running between the S and N poles of a magnet lying horizontally as shown in Figure below: 

The force on the wire due to the magnet is directed: 

fron N to S
 from S to N
 vertically downwards
 vertically upwards

An electric motor is a device which transforms: 

mechanical energy to electrical
 heat energy to electrical energy
 electrical energy to heat energy only
 electrical energy to mechanical energy

A magnetic field exerts no force on:

 an electrical charge moving perpendicular to its direction
 an unmagnetised iron bar
 a stationary electric charge
 a magnet

A horizontal wire carries a current as shown in Figure below between magnetic poles N and S: 

Is the direction of the force on the wire due to the magnet:

(a) in the direction the current
(b) vertically downwards
(c) opposite to the current direction
(d) vertically upwards 

In the simple electric motor of figure given below, the coil rotates anticlockwise as seen by the eye from the position X when current flows in the coil  

Is the current flowing clockwise or anticlockwise around the coil when viewed from above? 

Which way does the wire in the diagram below  tend to move? 

If the current in a wire is flowing in the vertically downward direction and a magnetic field is applied from west to east, what is the direction of force in the wire?

Which way does the wire in the diagram below tend to move? 

What is the force on a current-carrying wire that is parallel to a magnetic field? Give reason for your answer. 

A charged particle enters at right angles into a uniform magnetic field as shown: 

What should be the nature of charge on the particle if it begins to move in a direction pointing vertically our of the page due to its interaction with the magnetic field?  

Name the device which converts mechanical energy into electric energy.

Out of an A.C. generator and a D.C. generator:

 which one uses a commutator (split rings)?
 which one uses slip rings? 

Name the phenomenon which is made use of in an electric generator.

Name the rule which gives the direction of induced current.

What condition is necessary for the production of current by electromagnetic induction?

What type of generator is used at Power Stations?

What change should be made in an a.c. generator so that it may become a d.c. generator?

State whether the following statement are true or false: 

 A generator works on the principle of electromagnetic induction. 

State whether the following statement are true or false: 

A motor works on the principle electric generator? 

What is the function of brushes in an electric generator?

When a wire is moved up and down in a magnetic field, a current is induced in the wire. What is this phenomenon known as?

When current is 'switched on' and 'switched off' in a coil, a current is induced in another coil kept near it. What is this phenomenon known as?

What is the major difference between the simple alternator and most practical alternators? 

Why are Thermal Power Stations usually located near a river?

List three sources of magnetic fields.

Complete the following sentence: 

A generator with commutator produces ............... current. 

 Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.

 Explain the principle of an electric generator. 

 What is the difference between alternating current and direct current? 

 What type of current is given by (i) a dry cell, and (ii) a power House generator? 

State and explain Fleming's right hand rule.

Name and state the rule to find the direction of:  

current induced in a coil due to its rotation in a magnetic field. 

 force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it. 

 In what respect does the construction of an A.C. generator differ from that of a D.C. generator? 

 What normally drivers the alternators in a Thermal Power Station? What fuels can be used to heat eater in the boiler?

Draw the labelled diagram of an A.C. generator. With the help of this diagram, explain the construction and working of an A.C. generator. 

 What do you understand by the term "electromagnetic induction"? Explain with the help of a diagram. 

 Name one device which works on the phenomenon of electromagnetic induction. 

 Describe different ways to induce current in a coil of wire.

What do you understand by the terms 'direct current' and 'alternating current'? 

 Name some sources of direct current and some of alternating current. 

 State an important advantage of alternating current over direct current.

 What is the frequency of A.C. supply in India?

A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each______.

The phenomenon of electromagnetic induction is

The device used for producing electric current is called a ______.

The essential difference between an AC generator and a DC generator is that

When the switch S is closed in the figure given below, the pointer of the galvanometer moves to the right.  

If S is kept closed, will the pointer:

(a) return to zero?
(b) stay over on the right?
(c) move to the left and stay there
(d) move to and fro until S is opened

Each one of the following changes will increase emf (or voltage) in a simple generator except: 

(a) increasing the number of turns in the armature coil
(b) winding the coil on a soft iron armature
(c) increasing the size of the gap in which the armature turns
(d) increasing the speed of rotation

The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. The maximum deflection of the galvanometer was observed when the magnet was ______.

An electric generator converts:

(a) electrical energy into mechanical energy.
(b) mechanical energy into heat energy.
(c) electrical energy into chemical energy.
(d) mechanical energy into electrical energy. 

A d.c. generator is based on the principle of:

(a) electrochemical induction
(b) electromagnetic induction
(c) magnetic effect of current
(d) heating effect of current 

An induced current is produced when a magnet is moved into a coil. The magnitude of induced current does not depend on:  

(a) the speed with which the magnet is moved
(b) the number of turns of the coil
(c) the resistivity of the wire of the coil
(d) the strength of the magnet

The frequency of direct current (d.c.) is:

(a) 0 Hz
(b) 50 Hz
(c) 60 Hz
(d) 100 H 

The frequency of alternating current (a.c.) supply in India is:

(a) 0 Hz
(b) 50 Hz
(c) 60 Hz
(d) 100 Hz

A coil is connected to a galvanometer. When the N-pole of magnet is pushed into the coil, the galvanometer deflected to the right. What deflection, if any, is observed when:  

 the N-pole is removed?

A coil is connected to a galvanometer. When the N-pole of magnet is pushed into the coil, the galvanometer deflected to the right. What deflection, if any, is observed when: 

 the S-pole is inserted?

A coil is connected to a galvanometer. When the N-pole of magnet is pushed into the coil, the galvanometer deflected to the right. What deflection, if any, is observed when: 

the magnet is a rest in the coil? 

When the magnet shown in the diagram below is moving towards the coil, the galvanometer gives a reading to the right. 

() What is the name of the effect being produced by the moving magnet?
(2) State what happens to the reading shown on the galvanometer when the magnet is moving away from the coil.
(3) The original experiment is repeated. This time the magnet is moved towards the coil at a great speed. State two changes you would notice in the reading on the galvanometer.

If you hold a coil of wire next to a magnet, no current will flow in the coil. What else is needed to induce a current? 

The wire in Figure below is being moved downwards through the magnetic field so as to produce induced current. 

(a) moving the wire at a higher speed?
(b) moving the wire upwards rather than downwards?
(c) using a stronger magnet?
(d) holding the wire still in the magnetic field?
(e) moving the wire parallel to the magnetic field lines?

Two coils A and B of insulated wire are kept close to each other. Coil A is connected to a galvanometer while coil B is connected to a battery through a key. What would happen if: 

a current is passed through coil B by plugging the key?  

Explain your answer mentioning the name of the phenomenon involved.

Two coils A and B of insulated wire are kept close to each other. Coil A is connected to a galvanometer while coil B is connected to a battery through a key. What would happen if: 

the current is stopped by removing the plug from the key? 

Explain your answer mentioning the name of the phenomenon involved. 

A portable radio has a built-in transformer so that it can work from the mains instead of batteries. Is this a set-up or step down transformer? 

What name is given to the device which automatically cuts off the electricity supply during short-circuiting in household wiring?

What is the usual capacity of an electric fuse used (i) in the lighting circuit

What is the usual capacity of an electric fuse used  in the power circuit, of a small house?

Give the symbol of an electric fuse used in circuit diagrams.

State whether the following statement are true of false:  

A wire with a green insulation is usually the live wire. 

State whether the following statement are true of false: 

A miniature circuit breaker (MCB) works on the heating effect of current.

Along with live wire and neutral wire, a third wire is also used in domestic electric wiring. What name is given to this third wire? 

List the colours of the three wires in the cable connected to the plug of an electric iron.

What is the electric potential of the wire in a mains supply cable?

If fuse of 250 mA, 500 mA, 1 A, 5 A and 10 A were available, which one would be the most suitable for protecting an amplifier rated at 240 V, 180 W?  

When does an electric short circuit occur?

In which wire in a A.C. housing circuit is the switch introduced to operate the lights?

In household circuits, is a fuse wire connected in series or in parallel? 

What is the usually colour of the insulation of :

(a) live wire
(b) neutral wire
(c) earth wire?

What is the main propose of earthing an electrical appliance?

Give two reasons why different electrical appliances in a domestics circuit are connected in parallel.

How should the electric lamps in a building be connected so that the switching on or off in a room has no effect on other lamps in the same building?

Fill in the following blank with suitable words: 

 A fuse should always be places in the ........... wire of a mains circuit.

Fill in the following blank with suitable words: 

 The earth wire should be connected to the ........... of an appliance.