0What is a Circuit?
A circuit is a path through which electric current flows.
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It must be complete (closed) for current to flow.
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If the path is broken (open circuit), no current flows.
2. Basic Components of a Circuit
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Battery or Cell – provides electric energy to push electrons around the circuit.
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Resistor – limits the flow of current.
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Switch – can open or close the circuit.
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Wires – connect all the components.
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Load (like bulb, motor) – uses the electrical energy to do work.
3. Types of Circuits
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Series Circuit
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Components are connected one after the other.
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Current is the same through all components.
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If one component stops working, the whole circuit stops.
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Parallel Circuit
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Components are connected side by side.
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Current splits among the paths.
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If one component stops working, others continue to work.
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4. Semiconductor Devices in Circuits
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Diode
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Allows current to flow in one direction only.
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Used for rectification (AC to DC conversion).
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LED (Light Emitting Diode)
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Emits light when current passes through.
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Works only in one direction like a diode.
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Transistor
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Can amplify current or act as a switch.
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Essential in circuits for electronics like amplifiers and computers.
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Photodiode / Solar Cell
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Converts light into electricity.
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Used in solar panels and light sensors.
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5. Simple Circuit Examples
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Series Bulb Circuit – all bulbs glow with the same current.
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Parallel Bulb Circuit – bulbs glow independently; if one bulb goes out, others continue.
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Diode Circuit – allows current to flow in one direction; used in chargers.
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Transistor Switch – small current can control a bigger current in devices.
6. Key Points to Remember
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Current flows only in a closed circuit.
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Series: same current, voltage divides.
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Parallel: voltage same, current divides.
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Semiconductor devices (diodes, transistors, LEDs) are used to control and direct current in circuits.
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Circuits are the building blocks of all electronic devices.
