P4 - Electricity

Question 1

What causes a current to flow?

Answer 1

A circuit must have a potential difference for a current to flow

Question 2

What is an electric current?

Answer 2

The rate of the flow of electrons

Question 3

What does current depend on?

Answer 3

The greater the resistance of a component, the smaller the current for a given potential difference

Question 4

What is the unit of current?

Answer 4

Amps (A)

Question 5

What is the unit of charge flow?

Answer 5

Coulombs (C)

Question 6

What is the unit of potential difference?

Answer 6

Volts (V)

Question 7

What is the unit of resistance?

Answer 7

Ohms (Ω)

Question 8

How is current related to potential difference across a fixed resistor?

Answer 8

They are directly proportional as resistance is constant

Question 9

What happens to the resistance of a filament lamp as the temperature changes?

Answer 9

The resistance increases as the lamp gets hotter.
This is because the metal ions have more energy so vibrate more, making it harder for the electrons past

Question 10

What does a diode do?

Answer 10

A current can only flow through a diode in one direction. The reverse way has very high resistance

Question 11

How does the resistance of a thermistor change?

Answer 11

The resistance decreases as temperature increases

Question 12

How does the resistance of a LDR change?

Answer 12

The resistance decreases as light intensity increases

Question 13

How can a circuit be used to find the resistance of a component?

Answer 13

• Use an ammeter in series
• Use a voltmeter in parallel
• Use V = I X R

Question 14

What is the rule for current in a series circuit?

Answer 14

Current is the same everywhere

Question 15

What is the rule for potential difference in a series circuit?

Answer 15

The total potential difference of the power source is split among the components

Question 16

What is the rule for resistance in a series circuit?

Answer 16

The total resistance of components is the sum of the components’ resistances

Question 17

What is the rule for current in a parallel circuit?

Answer 17

The total current is split between the branches

Question 18

What is the rule for potential difference in a parallel circuit?

Answer 18

Potential difference is the same across each component

Question 19

What is the rule for resistance in a parallel circuit?

Answer 19

The total resistance is less than the smallest individual resistor