Electromagnetic induction, generators and transformers

Can you produce current in a wire with a magnet that is sitting still?

• Yes; having a magnet near a wire is enough to move the electrons

• No; the magnetic field has to be changing to excite the electrons

• No; magnets cannot create electricity

All of the following would increase the current induced by the magnet EXCEPT

• increasing the speed of the motion

• increasing the number of coils of wire

• increasing the resistance in the coils

• increasing the strength of the magnet

If a magnet is pushed into a coil, an electromotive force is induced across the coil. If the same magnet is pushed
into a coil with twice the number of loops,

• a. one-half as much electromotive force is induced.

• b. the same electromotive force is induced.

• c. twice as much electromotive force is induced.

• d. four times as much electromotive force is induced.

An electric generator

• converts mechanical energy into chemical energy

• converts chemical energy into electrical energy

• converts mechanical energy into gravitational potential energy

• converts mechanical energy into electrical energy

"AC" in an AC electric generator stands for

• alternating current

• alternative current

• actual current

• alternating cable

Device that uses electromagnetic induction to change the voltage of electric current.

• thermometer

• galvanometer

• electric transformer

• electric motor

For increasing the voltage ___________ is used.

• Step up transformer

• Step down transformer

• Current transformer

What is the primary function of a step-down transformer?

• Decrease voltage of AC power supply

• Convert DC power supply to AC

• Increase voltage of AC power supply

• Regulate the frequency of AC power supply

The number of loops in the primary and secondary coils is 100 and 350 respectively. The primary voltage is 200V. What is the voltage in the secondary coil?

• 400 V

• 500 V

• 600 V

• 700 V

The primary coil of a transformer has 10 loops and 1,200V. The secondary coil has a voltage of 2,400 V, what is the number of loops in this coil?

• 2

• 20

• 10

• 25