Advertisements
Advertisements
प्रश्न
Explain the construction and working of the following. Draw a neat diagram and label it.
Electric motor
Explain the construction and working of electric motor in short.
उत्तर
- Construction: Electric motor consists of the following parts:
- Rectangular coil: A large number of turns of insulated copper wire wound on iron core in rectangular shape forms a coil ABCD as shown in following figure.
- Strong magnet: The coil is placed in between two pole pieces (N and S) of a strong horse shoe magnet which provides a strong magnetic field. The sides AB and CD are perpendicular to the direction of the magnetic field.
- Split ring: It consists of two halves of a metallic ring (X and Y). The ends of the coil are connected to these rings. The outer conducting surfaces of spilt rings X and Y are in contact with the two stationary carbon brushes. Spilt rings reverse the direction of current in the coil.
- Brushes: Two carbon brushes E and F are used to press the split rings.
- Axle: The two halves of the rings have a resistive coating in their inner surfaces and are tightly fitted on the axle. The main function of an axle is to rotate with the coil.
- Battery: The battery supplies the current to the coil.
- Working:
- When the circuit is completed, the current passes through the brush E from A to B in branch AB.
- As, the magnetic field acts from north pole to south pole, according to Fleming’s left-hand rule, the force experienced by arm AB is in the downward direction and arm CD is in the upward direction.
- Both these forces are equal in magnitude and opposite in direction and hence, the coil rotates in an anticlockwise direction.
- After half rotation, the split rings X and Y come in contact with brushes E and F respectively.
- Again the current starts passing through the coil in opposite direction.
- The force acting on branch BA is upward and DC is downward, this force again moves the coil in an anticlockwise direction.
- This shows that the current in the loop ABCD is reversed after every half rotation, and the loop continues to rotate in the same direction.
- Thus, the coil rotates with the help of electrical energy.
APPEARS IN
संबंधित प्रश्न
Draw circuit symbols for
an open switch
A battery is to be formed by joining 3 dry cells with connecting wires. Show how will you connect the wires by drawing a diagram.
In an electric circuit, a battery and a bulb have been connected and the battery consists of two cells of equal potential difference. If the bulb is not glowing, then which tests will you perform in order to find out the reason for the bulb not glowing?
Explain the following:
Closed circuit
What is the potential difference?
How much is the potential difference between live and neutral wires?
Write scientific reason.
It is beneficial to carry electrical energy in AC form as it is carried over long distances.
What is the use of earthing wire?
______ is the device used to close or open an electric circuit.
The switch is used to close or open an electric circuit.
In the circuit shown, which switches (L,M or N) must be closed to light up the bulb?
In which of the following circuits are the bulb connected in series?
Higher Order Question
A student made a circuit by using an electric cell, a switch, a torch bulb (fitted in the bulb holder), and copper connecting wires. When he turned on the switch, the torch bulb did not glow at all. The student checked the circuit and found that all the wire connections were tight.
- What could be the possible reason for the torch bulb not glowing even when the circuit appears to be complete?
Three bulbs are connected end to end from the battery. This connection is called _______.
State whether true or false. If false, correct the statement.
Ammeter is connected in parallel in any electric circuit.
In a simple circuit, why does the bulb glow when you close the switch?
What is the role of the earth wire in domestic circuits?
Explain about domestic electric circuits. (circuit diagram not required)
Instead of metal wires, a jute string can be used to make a circuit.
In a circuit, if the key is in open (off) condition, then electricity will not flow.
In the following circuits (Figure), heat produced in the resistor or combination of resistors connected to a 12 V battery will be
 |
 |
 |
| (i) | (ii) | (iii) |
When an electric current flows through a copper wire AB as shown in Figure14.1, the wire
Three bulbs A, B, and C are connected in a circuit as shown in Figure 14.2. When the switch is ‘ON’
Name the device used these days in place of electric fuses in electrical circuits.
In an electric circuit a fuse is a _________ _______ to prevent possible fire.
What are the essential components of an electric circuit?
Will the bulb glow in the circuit shown in Fig. 12.6? Explain.
Overloading of electric circuits can lead to short-circuiting.
How is Joule's law effect useful in electric circuits where fuse is used as a safety device?
