Circuits

Question 1

Draw the circuit symbol for a switch.

Answer 1

Closed, Open

Question 2

Draw the circuit symbol for a cell.

Answer 2

+, -

Question 3

Draw the circuit symbol for a battery.

Answer 3

+, -, +, -

Question 4

Draw the circuit symbol for a lamp.

Answer 4

Question 5

Draw the circuit symbol for a fuse.

Answer 5

Question 6

Draw the circuit symbol for a voltmeter.

Answer 6

V

Question 7

Draw the circuit symbol for an ammeter.

Answer 7

A

Question 8

Draw the circuit symbol for a diode.

Answer 8

Question 9

Draw the circuit symbol for a resistor.

Answer 9

Question 10

Draw the circuit symbol for a thermistor.

Answer 10

Question 11

Draw the circuit symbol for a variable resistor.

Answer 11

Question 12

Draw the circuit symbol for an LDR.

Answer 12

Question 13

Draw the circuit symbol for an LED.

Answer 13

Question 14

What is electric current?

Answer 14

The flow of electrical charge.

Question 15

What can be said about the value of current at any point in a series circuit?

Answer 15

Current is the same at all points in a closed loop.

Question 16

What two factors does the current in a circuit depend on?

Answer 16

1. Potential Difference (V)
2. Resistance (R)

Question 17

What equation should be used to calculate potential difference if current and resistance are known? State the units for all 3 quantities.

Answer 17

V = IR
Potential Difference (V), Current (A), Resistance (Ω)

Question 18

What is an ‘Ohmic Conductor’? State the condition required.

Answer 18

• A conductor for which current and potential difference are directly proportional
• Resistance remains constant as current changes
• Temperature must be constant

Question 19

List four components for which resistance is not constant as current changes.

Answer 19

1. Lamps
2. Diodes
3. Thermistors
4. Light Dependent Resistors (LDRs)

Question 20

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

Answer 20

• Resistance increases
• Ions in metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance to current flow

Question 21

What is special about current flow through a diode?

Answer 21

• The current only flows in one direction
• Resistance is very high in the other direction, preventing current flow

Question 22

State what happens to the resistance of a thermistor as temperature increases.

Answer 22

The thermistor’s resistance decreases.

Question 23

Give two examples of when a thermistor may be used.

Answer 23

1. In a thermostat to turn a heater on below a certain temperature
2. In a freezer to turn on a cooler when the temperature becomes too high

Question 24

State what happens to the resistance of a LDR as light intensity decreases.

Answer 24

The LDR’s resistance increases.

Question 25

Give an application for a LDR.

Answer 25

* Street lamps or night lights * When light levels become too low, the light gains sufficient current to turn on

Question 26

What are the two ways that a component can be connected in a circuit?

Answer 26

1. Series (same loop) 2. Parallel (adjacent loop)

Question 27

How does the potential difference across two components vary when connected in series and parallel?

Answer 27

* Series: Total P.D is shared between components * Parallel: Each component gets the full P.D