Topic 10: Electricity And Circuits

Question 1

What are the 3 subatomic components that make up an atom?

Answer 1

• Electrons
• Protons
• Neutrons

Question 2

Describe the structure of an atom?

Answer 2

• neutrons and protons in the nucleus
• electrons surrounding the nucleus in shells

Question 3

In a closed circuit, what will there also be if there is a potential difference in the circuit?

Answer 3

Current

Question 4

How is current defined?

Answer 4

As the rate of flow of charge (or electrons) around a circuit

Question 5

What are the units of charge?

Answer 5

Coulombs, C

Question 6

What are the 2 ways that a component can be connected in a circuit?

Answer 6

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

Question 7

What is voltage also known as?

Answer 7

Potential difference

Question 8

How does the potential difference across 2 components vary when connected in series and parallel?

Answer 8

• In a series circuit the total P.D is shared between each component
• In a parallel circuit the P.D across each component is the same

Question 9

If 2 resistors are connected in parallel, what can be said about their combined total resistance?

Answer 9

Their total resistance is less than the smallest of the two individual resistances

Question 10

If 2 resistors are connected in series, what can be said about their combined total resistance?

Answer 10

Their total combined resistance is equal to the sum of the 2 individual resistances

Question 11

Where must a voltmeter be placed in a circuit?

Answer 11

In parallel with the component that is being measured

Question 12

What can a volt also be described as?

Answer 12

Joule per coulomb

Question 13

What is an electric current?

Answer 13

The rate or flow of charge

Question 14

What can be said about the value of current at any point in a single closed loop?

Answer 14

Current is the same at all point in a closed loop

Question 15

What 2 factors does the current in a circuit depend on?

Answer 15

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

Question 16

What is an ammeter and where must it be connected in a circuit?

Answer 16

An ammeter measures current, placed in series with the component it is required to measure

Question 17

What happens when current reaches a junction in a circuit?

Answer 17

Current is conserved, the total current remains the same and is split between the two branches

Question 18

How does resistance affect current in a circuit?

Answer 18

As the total resistance of a circuit increases, the current flowing through the circuit decreases

Question 19

How can the current in a circuit be varied?

Answer 19

Using a variable resistor

Question 20

How is total resistance affected by 2 resistors in series?

Answer 20

The total resistance increases, it is equal to the sum of the 2 resistors

Question 21

How is total resistance affected by 2 resistors in parallel?

Answer 21

The total resistance decreases, it is less than the resistance of the resistor with the lowest resistance

Question 22

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

Answer 22

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

Question 23

What are the 4 components for which resistance is not constant as current changes?

Answer 23

1. Filament lamps
2. Diodes
3. Thermistors
4. Light dependant resistors (LDRs)

Question 24

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

Answer 24

• Resistance increases
• Metal ions have more KE, so vibrate more, colliding more frequently with electrons as they flow through the metal
• This creates more resistance to current flow

Question 25

What is different about current flow through a diode?

Answer 25

The current only flows in one direction, resistance is very high in the other direction

Question 26

What happens to the resistance of a thermistor as temperature increases?

Answer 26

The thermistor’s resistance decreases