Electromagnetism

The direction of the magnetic field at point R caused by the current I in the wire shown is

• To the left

• To the right

• Into the page

• Out of the page

When using Fleming's left hand rule, what does the thumb represent?

• Current

• Force

• Magnetic field

Which coil will make the strongest electromagnet for a given flow of current?

• 10cm coil with 100 turns

• 5cm coil with 200 turns

• 10cm coil with 200 turns

• 20cm coil with 200 turns

Moving charges generate

• Magnetic fields

• Light

• Electric fields

• Current

Two magnetic fields make a

• Current

• Connection

• Force

• Giant magnetic field

• Allison

• Blanca

• Chithra

• None are correct

Lenz's law says

• Ohm's law is only applicable on earth

• An induced current always flows clockwise

• An induced current cant perform work

• An induced current always opposes the change that caused it

Ohm's law is

• V=IR

• I=ΔQ/t

• P=IV

• F=MA

Two bar magnets are to be cut in half along the dotted lines shown. None of the pieces are rotated. After the cut:

• The two halves of each magnet will attract each other

• The two halves of each magnet will repel each other

• The two halves of the top magnet will repel, the two halves of the bottom magnet will attract

• The two halves of the top magnet will attract, the two halves of the bottom magnet will repel

Answer explanation

When cutting a magnet, you must end up with two new magnets having 2 poles each. For the top magnet the current N and S must stay as is, so the left of center part becomes a S and the right of center part becomes a N. There are now two opposite poles that attract. For the bottom magnet, by slicing it down the center you now have two magnets on top of each other. The poles would not change their current locations so you have two north and two south poles near each other on top and bottom which makes repulsion

Rank the potential difference, ΔV, across the four resistors

• ΔV4R > ΔV3R > ΔV2R > ΔVR

• ΔV4R > ΔV3R > ΔV2R = ΔVR

• ΔV4R = ΔV3R > ΔVR > ΔV2R

• ΔV2R = ΔVR > ΔV3R > ΔV4R