Circuit symbols charge and current - Teacher Slides.pptx

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Circuit symbols, charge and current

Electricity

Lesson 1 of 10

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up

Electricity

Lesson 1 of 10

Answer each one, then check.

1

What is the unit of current?

2

What is the unit of time in physics calculations?

3

Which particles carry current in a metal wire?

4

What does a battery provide?

5

Convert 2 minutes to seconds.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up - Answers

Electricity

Lesson 1 of 10

1

What is the unit of current?

The ampere (A)

2

What is the unit of time in physics calculations?

The second (s)

3

Which particles carry current in a metal wire?

Electrons

4

What does a battery provide?

A potential difference (a push for charge)

5

Convert 2 minutes to seconds.

120 s

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Learning Objectives

Electricity

Lesson 1 of 10

1

Draw and interpret circuit diagrams using standard symbols.

2

State that a source of potential difference is needed to make charge flow in a closed circuit.

3

Recall and apply Q = It.

4

State that the current has the same value at any point in a single closed loop.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Electricity

Lesson 1 of 10

CHARGE AND CURRENT

charge flow = current × time Q = It

Electric current is a flow of electrical charge. The size of the current is the rate of flow of charge. Charge is in coulombs (C), current in amperes (A) and time in seconds (s).

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Standard Circuit Symbols

Electricity

Lesson 1 of 10

Learn to draw these quickly and neatly.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Drawing a Circuit Diagram

Electricity

Lesson 1 of 10

Use a ruler and standard symbols.

1

Start with the power supply

Draw a cell or battery.

2

Add components in series

Draw straight lines with square corners; no gaps.

3

Add the ammeter in series

It goes in the main loop where you want to measure current.

4

Add the voltmeter in parallel

It goes across the component you are measuring.

5

Check

Every component is joined by lines and the loop is closed.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Charge Flow

Electricity

Lesson 1 of 10

A current of 3.0 A flows through a lamp for 20 s. Calculate the charge that flows.

1

Write the equation

Q = It

2

Substitute

Q = 3.0 × 20

3

Answer

Q = 60 C

ANSWER

60 coulombs

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Finding the Current

Electricity

Lesson 1 of 10

240 C of charge flows through a heater in 2 minutes. Calculate the current.

1

Convert the time

2 min = 120 s

2

Rearrange

I = Q ÷ t

3

Substitute

I = 240 ÷ 120

4

Answer

I = 2.0 A

ANSWER

2.0 A

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Key Ideas

Electricity

Lesson 1 of 10

Learn these.

A source of pd is needed

For charge to flow round a closed circuit there must be a source of potential difference, such as a cell.

Current in a series loop

The current has the same value at every point in a single closed loop.

Current is not used up

Charge keeps flowing round the loop; the components transfer energy from the charge.

Ammeter and voltmeter

Ammeter in series measures current. Voltmeter in parallel measures pd.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Key Terms

Electricity

Lesson 1 of 10

Electric current

The rate of flow of electrical charge.

Charge

A property of matter that can be positive or negative; measured in coulombs.

Ampere

The unit of current; one coulomb per second.

Coulomb

The unit of charge.

Ammeter

Measures current; connected in series.

Potential difference

The energy transferred per unit of charge; measured in volts.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Electricity

Lesson 1 of 10

YOUR TASK

Circuit Doodles

12 minutes

Draw circuit diagrams for: (a) a cell, a switch and a lamp in series; (b) the same circuit with an ammeter to measure the current in the lamp and a voltmeter to measure the pd across it.

1

Draw the loop with a ruler.

2

Add the meters in the right way.

WHAT A GOOD ANSWER SHOWS

(a) A loop containing a cell, closed switch and lamp. (b) The ammeter is in the loop (series); the voltmeter is drawn in parallel with the lamp only.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Can I...?

Electricity

Lesson 1 of 10

Recognise standard circuit symbols.

Draw a series circuit.

Place an ammeter and voltmeter correctly.

Use Q = It.

Rearrange for current or time.

Convert minutes to seconds.

Explain why current is the same round a series loop.

State what is needed for charge to flow.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Summary & Exam Focus

Q = It.

Symbols: cell, lamp, ammeter (A), voltmeter (V), and so on.

Ammeters in series, voltmeters in parallel.

Current is the same at every point in a series loop.

EXAM FOCUS

A current of 0.40 A flows for 30 s. Calculate the charge that flows. (2 marks)

Write the equation, substitute, and include the unit C.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Exam Practice: Circuit symbols, charge and current

Electricity

Lesson 1 of 10

Answer all questions. Use the mark allocation as a guide to how much to write. · 15 minutes

Question 1 · 2 marks · Calculate

A current of 0.40 A flows through a lamp for 30 s. Calculate the charge that flows through the lamp. Use the equation: charge flow =…

Question 2 · 4 marks · Draw

Draw a circuit diagram to show a cell, a switch and a lamp connected in series, with an ammeter to measure the current through the lamp and…

Question 3 · 3 marks · Calculate

180 C of charge flows through a heater in 1.0 minute. Calculate the current in the heater.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Exam Practice: Circuit symbols, charge and current (cont.)

Electricity

Lesson 1 of 10

Question 4 · 2 marks · Explain

In a series circuit, ammeter A1 reads 0.50 A. A second ammeter, A2, is on the other side of a lamp. What does A2 read? Explain your answer.

Question 5 · 3 marks · Calculate

A charge of 12 C flows through a resistor when the current is 0.50 A. Calculate the time for which the current flows.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 1 · 2 marks · Calculate

Electricity

Lesson 1 of 10

“

A current of 0.40 A flows through a lamp for 30 s. Calculate the charge that flows through the lamp. Use the equation: charge flow = current × time

HOW TO ANSWER IT

Command word: Calculate. Worth 2 marks, so plan before writing.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 1 · mark scheme

Electricity

Lesson 1 of 10

2 marks available. Award a mark for each point made.

Correct substitution

1 mark

12 C

1 mark

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 2 · 4 marks · Draw

Electricity

Lesson 1 of 10

“

Draw a circuit diagram to show a cell, a switch and a lamp connected in series, with an ammeter to measure the current through the lamp and a voltmeter to measure the potential difference across the lamp. Use the correct circuit symbols.

HOW TO ANSWER IT

Command word: Draw. Worth 4 marks, so plan before writing.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 2 · mark scheme

Electricity

Lesson 1 of 10

4 marks available. Award a mark for each point made.

Cell, switch and lamp in a closed series loop

1 mark

Ammeter in series

1 mark

Voltmeter in parallel with the lamp

1 mark

All symbols correct

1 mark

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 3 · 3 marks · Calculate

Electricity

Lesson 1 of 10

“

180 C of charge flows through a heater in 1.0 minute. Calculate the current in the heater.

HOW TO ANSWER IT

Command word: Calculate. Worth 3 marks, so plan before writing.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 3 · mark scheme

Electricity

Lesson 1 of 10

3 marks available. Award a mark for each point made.

Converts 1.0 minute to 60 s

1 mark

Correct substitution

1 mark

3.0 A

1 mark

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 4 · 2 marks · Explain

Electricity

Lesson 1 of 10

“

In a series circuit, ammeter A1 reads 0.50 A. A second ammeter, A2, is on the other side of a lamp. What does A2 read? Explain your answer.

HOW TO ANSWER IT

Command word: Explain. Worth 2 marks, so plan before writing.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 4 · mark scheme

Electricity

Lesson 1 of 10

2 marks available. Award a mark for each point made.

0.50 A

1 mark

Current is the same at every point in a series loop

1 mark

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 5 · 3 marks · Calculate

Electricity

Lesson 1 of 10

“

A charge of 12 C flows through a resistor when the current is 0.50 A. Calculate the time for which the current flows.

HOW TO ANSWER IT

Command word: Calculate. Worth 3 marks, so plan before writing.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 5 · mark scheme

Electricity

Lesson 1 of 10

3 marks available. Award a mark for each point made.

Rearranges to t = Q ÷ I

1 mark

Correct substitution

1 mark

24 s

1 mark

openrevise.com