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Electricity - The effect of voltage and number of components on a circuit

Grade 5IGCSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Voltage (VV) is the measure of the 'push' or electrical force provided by a power source, such as a battery or cell, to move charge through a circuit.

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The brightness of a bulb depends on the amount of electrical current flowing through it. Current is measured in Amperes (AA).

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Increasing the number of cells (increasing total voltage) in a series circuit increases the current, making bulbs glow brighter and motors spin faster.

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Increasing the number of components (like bulbs) in a series circuit increases the total resistance (RR), which reduces the current and makes bulbs glow dimmer.

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In a series circuit, the total voltage provided by the cells is shared among all the components. For example, if there are nn identical bulbs, each receives 1n\frac{1}{n} of the total voltage.

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If the voltage is too high for a component (e.g., a 1.5V1.5V bulb connected to a 9V9V battery), the filament in the bulb may break because too much current flows through it.

📐Formulae

V=I×RV = I \times R

Vtotal=V1+V2+V3+...V_{total} = V_1 + V_2 + V_3 + ...

I∝VI \propto V

I∝1RI \propto \frac{1}{R}

💡Examples

Problem 1:

A simple circuit contains one 1.5V1.5V cell and one bulb. If you add two more 1.5V1.5V cells in series, what will happen to the brightness of the bulb?

Solution:

The bulb will shine significantly brighter.

Explanation:

By adding more cells, the total voltage increases from 1.5V1.5V to 1.5V+1.5V+1.5V=4.5V1.5V + 1.5V + 1.5V = 4.5V. A higher voltage pushes more current through the circuit, increasing the energy delivered to the bulb.

Problem 2:

A circuit is powered by a 3V3V battery and has one bulb. If a second identical bulb is added into the circuit in series, how does the brightness change?

Solution:

Both bulbs will be dimmer than the single bulb was originally.

Explanation:

Adding a second bulb increases the total resistance of the circuit. Furthermore, the 3V3V from the battery is now shared between two bulbs, meaning each bulb only receives 1.5V1.5V (3V÷2=1.5V3V \div 2 = 1.5V).

Problem 3:

If a circuit has a 9V9V battery and three identical bulbs in series, how much voltage does each bulb receive?

Solution:

Each bulb receives 3V3V.

Explanation:

In a series circuit, the voltage is shared equally among identical components. Calculation: 9V3 bulbs=3V\frac{9V}{3 \text{ bulbs}} = 3V per bulb.

The effect of voltage and number of components on a circuit Revision - Grade 5 Science IGCSE