Potential difference
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Lesson notes
What is Potential Difference?
- A battery or power supply gives **energy** to each charge in a circuit.
- Electrical components (e.g., lamps, resistors) **use** this energy, transferring it to other stores.
- **Potential difference** (voltage) measures the difference in energy that charges have between two points in a circuit.
- Units: **volts (V)**.
- Measured by a **voltmeter** placed **in parallel** across the component.
- Circuit symbol for a voltmeter: a circle with a **V** inside.
Potential Difference in Series Circuits
- In a **series circuit**, the total potential difference is **split** across all components.
- For two identical resistors in series, each gets **half** the total voltage (e.g., 5 V each from a 10 V cell).
- The sum of potential differences across each component equals the total potential difference of the supply.
Potential Difference in Parallel Circuits
- In a **parallel circuit**, each branch receives the **full** potential difference of the supply.
- Potential difference across each parallel branch is **the same** (e.g., 10 V across each branch from a 10 V cell).
- If a branch has multiple components in series, the voltage is **shared** among them (e.g., two bulbs in a branch each get 5 V).
- A lamp with a **higher** potential difference across it glows **brighter**.
Advantages of Parallel Circuits for Lamps
- Each lamp receives the **full** potential difference, so it is **brighter** than in series.
- Lamps can be turned **on and off independently** if each branch has its own switch.
- A circuit must be **complete** for current to flow.
Lamp Ratings
- The **lamp rating** is the **maximum** potential difference that is safe to put across a lamp without breaking it.
- Exceeding the rating can damage the lamp.
Series circuit: two identical resistors share the 10 V potential difference equally (5 V each).
Parallel circuit: each lamp receives the full 10 V potential difference.
Parallel branch with two bulbs in series: each bulb gets 5 V (half the branch voltage).
Slides
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Practice questions
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1.What is the unit of potential difference?
Easy- AVolts
- BAmperes
- COhms
- DWatts
2.Which instrument is used to measure potential difference?
Easy- AAmmeter
- BVoltmeter
- COhmmeter
- DGalvanometer
3.How is a voltmeter connected in a circuit?
Easy- AIn series
- BIn parallel
- CEither series or parallel
- DNot connected
4.In a series circuit, how is the potential difference distributed?
Easy- ASame across all components
- BSplit across components
- CZero across each component
- DEqual to the current
5.A 10 V cell is connected to two identical resistors in series. What is the potential difference across each resistor?
Medium- A10 V
- B5 V
- C20 V
- D0 V
6.In a parallel circuit with a 10 V cell and two branches, what is the potential difference across each branch?
Medium- A5 V
- B10 V
- C20 V
- D0 V
7.Which statement about lamps in parallel is correct?
Medium- AEach lamp gets less than the full voltage
- BIf one lamp breaks, the others go out
- CEach lamp can be controlled independently with a switch
- DThe lamps are dimmer than in series
8.What does a lamp's rating indicate?
Medium- AThe current it draws
- BThe maximum safe potential difference
- CThe resistance of the lamp
- DThe brightness of the lamp
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