An electron is released from rest in a region of space where an electric field E

Question

An electron is released from rest in a region of space where an electric field E points up the page and a magnetic field B points into the page. Which path best represents the motion of the electron after it is released? Three long parallel wires carry the same current I_1 = I_2 = I_3, but I_1 is opposite to I_2 and I_3. All the wires lie in the same plane, and I_2 lies directly between I_1 and I_3, a distance R from both. What is the direction of the net force on I_3 due to the other two wires? (a) no net force (b) to the right (c) to the left (d) into the page (e) out of the page A loop of wire moves toward a straight wire carrying a current I, as shown in the figure to the right. The direction of the induced current in the loop is _____, which results in a net force on the loop _____ (a) clockwise, to the left (b) counterclockwise, to the left (c) clockwise, to the right (d) counterclockwise, to the right (e) no induced current, no force The primary side of a transformer has a voltage of 200 V with a current of 5 A. If the primary side has 100 loops and the current in the secondary side is 50 A, the secondary has _____ loops and a voltage of _____. (a) 10, 20 V (b) 10, 2000 V (c) 100, 20 V (d) 1000, 20 V (e) 1000, 2000 V A sample of some unknown substance is repelled by a permanent ferromagnet. This material must be _____ and its relative permeability must be _____. (a) diamagnetic, 1 (e) ferromagnetic, > 1

Explanation / Answer

1. part d is best option as v=0 so no magnetic force and electron moves in the opposite direction of the electric field.

2.c There will be attraction between 2 and 3 and repulsion between 1 and 3 but attraction will be dominent as 2 and 3 are closer so force will be towards left

3. d is correct as the magnetic flux increases into the plane so from lenz's law anticlockwise current will flow against the changing magnetic field now since nearer part will have repulsion and farther part will have attraction so there will be a net repulsion as repulsion dominates so force will be to the right

4 Since for ideal transformer VI= constant so V1I1=V2I2=> V2=20 V and n=V1/V2=10 so a is correct

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