Topic 13 - EM Induction

Question 1

What is Electromagnetic Induction?

Answer 1

• Creating an electric current by moving a magnet or a coil of wire relative to each other

Question 2

Factors Affecting Potential Difference in Electromagnetic Induction:

Answer 2

• Rate of Change of all Magnetic Field passing through a surface
• Number of Turns in the Coil
• Strength of the Magnetic Field (MFD)
• Area of the Coil

Question 3

How do the magnetic field produced oppose the original change ?

Answer 3

• After the (original) change of the magnets and the coil of wire, the coil produces an opposite magnetic field

Question 4

Electromagnetic induction is used in alternators to generate current which:

Answer 4

• alternates in direction

Question 5

Electromagnetic induction is used in
dynamos to generate current which:

Answer 5

• is direct

Question 6

How do microphone convert the pressure variations in sound waves into variations in current in electrical circuits?

Answer 6

• Sound waves cause diaphragm to vibrate
• This causes coil (connecting to microphone) to vibrate
• Coil cuts through field lines, inducing an alternating p.d, and therefore, alternating current

Question 7

How can an alternating current in one circuit induce a current in another circuit in a transformer

Answer 7

• Creates a magnetic field when current flows through. This induces a voltage in the second coil

Question 8

A transformer can change what in an alternating voltage?

Answer 8

• its size

Question 9

Why is electrical energy transferred at high voltages from power stations, and then transferred at lower voltages in each locality?

Answer 9

• improves the efficiency by reducing heat loss in transmission lines

Question 10

Why are step-up and step-down transformers used in the transmission of electricity in the national grid

Answer 10

Step up:
- Before entering national grid
- Reduces energy losses due to resistance in the transmission lines
Step down:
- Nearing destinations
- Make the electricity safe and suitable for use