Chapter 4 Electric Circuits

Question 1

4.1 What do the same charges do

Answer 1

They repel each other

Question 2

4.1 What do different charges do (i.e. positive or negative)

Answer 2

They attract each other

Question 3

4.1 What do insulating materials do when they are rubbed together

Answer 3

They are charged. An example is a polythylene rod being rubbed a cloth.

Question 4

4.1 The force between two charged objects are contact or non-contact

Answer 4

They are non-contact forces.

Question 5

4.2 What is an electric current?

Answer 5

It is a flow of charge

Question 6

4.2 Charge flow equation

Answer 6

Current x time taken

Question 7

4.3 What does the ammeter measure

Answer 7

The current in amps

Question 8

4.3 What does the voltmeter measure

Answer 8

The potential difference. It must be parallel to the torch bulb so it measures the potential difference across.

Question 9

4.3 Potential difference equation

Answer 9

Energy transferred (J) /charge (coulombs)

Question 10

4.3 Resistance (ohms) equation

Answer 10

Potential difference volts /current amps

Question 11

4.4 What is a light-emitting diode (LED)

Answer 11

A diode that emots light when current passes through in a forward direction.

Question 12

4.4 Diode definition

Answer 12

A non-ohmic conductor

Question 13

4.4 What is a thermistor

Answer 13

Temperature-dependent resistor

Question 14

4.4 What happens to the resistance of the light-dependent resistor when the light intensity increases?

Answer 14

The resistance decreases

Question 15

4.5 What happens to the current in a series circuit?

Answer 15

The same current passes throught the component (doesn’t change)

Question 16

4.5 What happens to the total potential difference of the power supply in a series circuit

Answer 16

It is shared between the components

Question 17

4.5 How to find the potential difference using the cells in a circuit

Answer 17

Find the sum of the potential difference

Question 18

4.5 How to find the total resistance in a series circuit?

Answer 18

R1+R2

Question 19

4.6 How to find the current in a whole parallel circuit?

Answer 19

Sum of the currents in the separate branches

Question 20

4.6 How to find the potential difference across each component

Answer 20

The potential difference across each component is the same

Question 21

4.6 How to find the resistance in a parallel circuit

Answer 21

Use the equation:
Current = Potential difference/resistance
You must re-arrange it

Question 22

4.6 What happens when you add more resistors in a parallel circuit

Answer 22

Adding more resistors decreases the total resistance because the total resistance because the total current the through the resistors is increased.