9.2Physics 03. Electricity And Magnetism
Know how to measure current and voltage in series and parallel… — Cambridge Checkpoint Science 0893 Revision Notes & Topical Questions
5 min read 10 parts Lesson 2 of 5 1 quiz
Lesson summary
9.2 Measuring current and voltage in series and parallel circuits — CHECKPOINT - Lower Secondary Science 0893 notes: Know how to measure current and voltage in series and parallel circuits and the rules for each.Current — measured in amps (A) with an ammeter.Connection — the amme…
- Series circuit
- Adding lamps
- Adding cells
- Adding a branch
- Voltmeter — measures the voltage across a component.It is connected in parallel with the component
- Voltage — the voltages across the components add up to the supply voltage
Section 1 of 10Measuring current
Current
- Current measured in amps (A) with an ammeter.
Connection
- Connection the ammeter is connected in series with the component.
- It is placed in the circuit so that the current flows through it.
Section 2 of 10Measuring voltage
Voltage
- Voltage a measure of the electrical energy in a circuit, in volts (V).
- A cell supplies 1.5 V and mains supply is 220 to 240 V in most countries.
Voltmeter
- Voltmeter measures the voltage across a component.
- It is connected in parallel with the component.
Section 3 of 10Ammeter and voltmeter compared
| Meter | Measures | Unit | Connected |
|---|---|---|---|
| Ammeter | Current through a component | Amp, A | In series |
| Voltmeter | Voltage across a component | Volt, V | In parallel |
Section 4 of 10Series circuits
Series circuit
- Series circuit all the components are connected end to end in one path.
Current
- Current the current is the same everywhere in a series circuit.
Voltage
- Voltage the voltages across the components add up to the supply voltage.
Switch
- Switch opening it stops the whole circuit.
Adding lamps
- Adding lamps the voltage is shared so each lamp gets less and the current decreases.
Adding cells
- Adding cells the supply voltage and the current both increase.
Section 5 of 10Parallel circuits
Parallel circuit
- Parallel circuit there is more than one path, called a branch, for the current.
Current
- Current the current through the cell equals the total of the currents in the branches.
- With identical lamps the current divides equally between the branches.
Voltage
- Voltage the voltage across each branch equals the supply voltage.
Adding a branch
- Adding a branch it gives another path, so the current from the cell increases.
Section 6 of 10Series compared with parallel
| Feature | Series circuit | Parallel circuit |
|---|---|---|
| Paths | One | More than one |
| Current | Same everywhere | Shared between branches, total at the cell |
| Voltage | Shared between components | Same across each branch |
| If one component fails | All stop | Other branches continue |
Section 7 of 10Advantages of parallel circuits
1
Components can be switched on and off separately, with a switch in each branch.
2
If one component stops working the others keep working.
3
A switch between the cell and the branches switches everything on or off together.
4
Examples are car headlamps and a string of lamps.
Section 8 of 10Rule for calculating a missing current
Rule for calculating a missing current
Write the total current through the cell.
Add all the known branch currents.
Subtract the sum from the total to get the missing branch current.
Section 9 of 10Key terms
| Term | Meaning |
|---|---|
| Ammeter | Meter that measures current, connected in series. |
| Voltmeter | Meter that measures voltage, connected in parallel. |
| Series circuit | Circuit with components connected one after another. |
| Parallel circuit | Circuit with components on separate branches. |
| Branch | One of the paths in a parallel circuit. |
| Voltage | A measure of the electrical energy supplied or changed in a circuit. |
Section 10 of 10Exam technique
1
Current is shared in a series circuit — it is the same everywhere in a series circuit.
2
Voltage is shared in a parallel circuit — each branch has the full supply voltage.
3
A voltmeter is connected in series — it is connected in parallel.
4
Current gets used up by components — the same current returns to the cell.
Marked practiceQuizzes for this lesson
Last updated: