Physics Section 2

Question 1

What is the difference between alternating current and direct current?

Answer 1

An alternating current changes direction rapidly and goes backwards and forwards; direct current travels in one direction only

Question 2

What is the formula for potential difference (Voltage)

Answer 2

Potential difference = current x resistance

Question 3

What is the formula for power?

Answer 3

Power = potential difference x current
or
resistance x current^2

Question 4

What is direct current?

Answer 4

d.c.:
- Has a direct potential difference, always positive or negative, constant
- Is the type that’s supplied by cells and batteries

Question 5

What is alternating current?

Answer 5

a.c.:
- Has an alternating potential difference, alternates from positive to negative
- Is the type of current used my mains electricity

Question 6

What colours are the wires in a three pin plug?

Answer 6

• Earth wire: green and yellow
• Neutral wire: blue - carries current away
• Live wire: brown - carries current to the appliance

Question 7

What is the equation for charge flow?

Answer 7

Charge flow = current x time
or
Q = I x t (t in s)

Question 8

What is the equation for voltage

Answer 8

Voltage = Amps x Resistance
or
V = I x R

Question 9

What is voltage?

Answer 9

The amount of energy electrons give to components

Question 10

What is the equation for current?

Answer 10

Current = Voltage / Resistance

Question 11

label this diagram

Answer 11

Question 12

What is the purpose of Step down transformers?

Answer 12

• They reduce the potential difference from the cables to a much lower value for domestic use

Question 13

Give two ways the National Grid is designed to be efficient:

Answer 13

• Low amps and high volts to reduce the amount of energy lost to heat
• Power is generated at large power stations