E - Electricity

Question 1

How does temperature affect resistance? (3)

Answer 1

Heat increases resistance

because the friction exerted by electrons transfers energy to the metal atoms

which vibrate more making it more difficult for electrons to flow through the wire

Question 2

How does current flow through a diode?

Answer 2

in one direction only

Question 3

What happens to resistance of an LDR as light intensity increases?

Answer 3

resistance decreases

Question 4

What are LDRs used for in circuits?

Answer 4

e.g. to switch lights on when it gets dark

Question 5

Ohm’s law states that…

1. ? is directly proportional to ?
2. if…

Answer 5

1. voltage is directly proportional to current
2. if temperature remains constant

Question 6

Total resistance in series is calculated by…

Answer 6

R1 + R2 = Total Resistance

Question 7

The total resistance ? as it ? in parallel

Answer 7

decreases as resistance increases in parallel

Question 8

Series:

1. stays the same
2. shared
3. resistance

Answer 8

1. current
2. voltage / potential difference
3. added

Question 9

Parallel:

1. stays the same
2. shared

Answer 9

1. voltage / potential difference
2. current

Question 10

Main electricity voltage and frequency (Hz)

Answer 10

230V + 50Hz

Question 11

Plug:

1. blue wire
2. green and yellow wire
3. brown wire

Answer 11

Plug:

1. neutral wire
2. earth wire
3. live wire

Question 12

National grid order:

Answer 12

power station, step up transformer, cables, step down transformer, homes

Question 13

Why transport at high voltage?

1. equation
2. min max
3. why?

Answer 13

1. Power loss = (Current)^2 x R
2. min current, max voltage
3. same energy per second, but reduced heating of cable (current is low so less interact with metal ions in wire)