Advertisements
Advertisements
Question
A straight horizontal conducting rod of length 0.45 m and mass 60 g is suspended by two vertical wires at its ends. A current of 5.0 A is set up in the rod through the wires.
(a) What magnetic field should be set up normal to the conductor in order that the tension in the wires is zero?
(b) What will be the total tension in the wires if the direction of current is reversed keeping the magnetic field same as before?
(Ignore the mass of the wires) g = 9.8 m s–2.
Solution
Length of the rod, l = 0.45 m
Mass suspended by the wires, m = 60 g = 60 × 10−3 kg
Acceleration due to gravity, g = 9.8 m/s2
Current in the rod flowing through the wire, I = 5 A
(a) Magnetic field (B) is equal and opposite to the weight of the wire i.e.,
BIl = mg
∴ B = `"mg"/"Il"`
= `(60 xx 10^-3 xx 9.8)/(5 xx 0.45)`
= 0.26 T
A horizontal magnetic field of 0.26 T normal to the length of the conductor should be set up in order to get zero tension in the wire. The magnetic field should be such that Fleming’s left-hand rule gives an upward magnetic force.
(b) If the direction of the current is reversed, then the force due to the magnetic field and the weight of the wire act in a vertically downward direction.
∴ Total tension in the wire = BIl + mg
= 0.26 × 5 × 0.45 + (60 × 10–3) × 9.8
= 1.176 N
APPEARS IN
RELATED QUESTIONS
Sketch the change in flux, emf and force when a conducting rod PQ of resistance R and length l moves freely to and fro between A and C with speed v on a rectangular conductor placed in uniform magnetic field as shown in the figure
Which of the following particles will have minimum frequency of revolution when projected with the same velocity perpendicular to a magnetic field?
A particle moves in a region with a uniform magnetic field and a parallel, uniform electric field. At some instant, the velocity of the particle is perpendicular to the field direction. The path of the particle will be
A vertical wire carries a current in upward direction. An electron beam sent horizontally towards the wire will be deflected
A long, straight wire is fixed horizontally and carries a current of 50.0 A. A second wire having linear mass density 1.0 × 10−4 kg m−1 is placed parallel to and directly above this wire at a separation of 5.0 mm. What current should this second wire carry such that the magnetic repulsion can balance its weight?
Consider the situation shown in the figure. Suppose the circular loop lies in a vertical plane. The rod has a mass m. The rod and the loop have negligible resistances but the wire connecting O and C has a resistance R. The rod is made to rotate with a uniform angular velocity ω in the clockwise direction by applying a force at the midpoint of OA in a direction perpendicular to it. Find the magnitude of this force when the rod makes an angle θ with the vertical.
Two infinitely long current carrying conductors X and Y are kept parallel to each other, 24 cm apart in a vacuum. They carry currents of 5A and 7A respectively, in the same direction, as shown in the figure below. Find the position of a neutral point, i.e., a point where resultant magnetic flux density is zero. (Ignore earth’s magnetic field).
An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?
When a magnetic compass needle is carried nearby to a straight wire carrying current, then
- the straight wire cause a noticeable deflection in the compass needle.
- the alignment of the needle is tangential to an imaginary circle with straight wire as its centre and has a plane perpendicular to the wire.
A small object with charge q and weight mg is attached to one end of a string of length ‘L’ attached to a stationary support. The system is placed in a uniform horizontal electric field ‘E’, as shown in the accompanying figure. In the presence of the field, the string makes a constant angle θ with the vertical. The sign and magnitude of q ______.
