Question

5.) Two concentric current loops lie in the same plane. The smaller loop has a radius of 3.5 cm and a current of 12 A. The bigger loop has a current of 20 A . The magnetic field at the center of the loops is found to be zero. What is the radius of the bigger loop?

9.) An 1100-turn coil of wire that is 2.3 cm in diameter is in a magnetic field that drops from 0.15 T to 0 T in 11 ms . The axis of the coil is parallel to the field. What is the emf of the coil?

The magnetic field 10 cm from a wire carrying a 1 A current is 2 μT. What is the field 2 cmcm from the wire?

The earth's magnetic field strength is 5.0×10−5T . How fast would you have to drive your car to create a 3.0 V motional emf along your 1.0 m -long radio antenna? Assume that the motion of the antenna is perpendicular to B⃗ B→.

Answer 1

1) magnetic field due to circular loop at its center is given by,

so, in order to cancel the net magnetic field at center magnetic field due to each loop must be equal in magnitude and direction of current must be opposite so,

so,

so putting values we get,

r2=5.83cm

2) emf of coil is given by

so rate of change of magnetic field is,

area A=0.00166 m^2

N=1600

putting all values we get,

3) magnetic field due to wire is given by,

so, at r=2 cm is by putting values we get

B=10 μT

4) emf due to earth is given by

v is velocity and l is length

so,

so putting values we get,