Electromagnetic induction

Question 1

When is voltage induced in a conductor or coil?

Answer 1

When it moves through a magnetic field or when a magnetic field moves through it

Question 2

Factors that affect the size of induced currents

Answer 2

• Number of turns
• Speed of motion
• Strength of magnetic field

Question 3

How does a transformer work?

Answer 3

1. AC passing through the primary coil will induce an alternating magnetic field that goes through the soft iron core
2. Magnetic field lines pass through the secondary coil
3. Due to the change in magnitude and direction, the field lines are constantly “cutting” the coil
4. This induces a voltage across the coil which induces a current

Question 4

How does a step-up transformer work?

Answer 4

Has a low input voltage into the primary coil. The secondary coil has more turns than the primary coil resulting in the secondary coil having a higher voltage

Question 5

How does a step-down transformer work?

Answer 5

Has a high input voltage into the primary coil. The secondary coil has less turns than the primary coil resulting in the secondary coil having a lower voltage

Question 6

When is a step-up transformer used?

Answer 6

Before long distance transmission

Question 7

What happens during long distance transmission?

Answer 7

High voltage = low current because input power = output power assuming 100% efficiency. This reduces energy loss due to heat

Question 8

Why is a step-down transformer needed before reaching residential areas and again before reaching homes?

Answer 8

Safety

Question 9

V_p/V_s

Answer 9

N_p/N_s