Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
An electric cell is a device that produces electricity from chemicals stored inside it. It has two terminals: a positive terminal () and a negative terminal ().
The electric bulb consists of a glass case fixed on a metallic base. Inside, it has a thin wire called the filament, usually made of tungsten, which glows when current () passes through it.
A simple electric circuit is a closed path through which electric current flows. Current flows from the positive () terminal to the negative () terminal of the electric cell.
An electric switch is a simple device that either breaks the circuit (Open Circuit) or completes it (Closed Circuit).
Heating Effect: When an electric current passes through a wire, the wire gets heated. In a bulb, the filament heats up to a very high temperature () until it begins to glow.
Magnetic Effect: A wire carrying an electric current behaves like a magnet. This was first observed when a compass needle showed deflection when placed near a current-carrying wire.
Conductors are materials that allow electric current to pass through them (e.g., Copper, Aluminum, Iron), while insulators do not allow current to pass (e.g., Rubber, Plastic, Wood).
📐Formulae
💡Examples
Problem 1:
A bulb in a closed circuit does not glow. Upon inspection, the filament is found to be broken. Explain why the bulb does not glow using circuit terminology.
Solution:
When the filament is broken, the bulb is said to be 'fused'.
Explanation:
A broken filament means there is a gap in the path of the electricity. This creates an 'Open Circuit', preventing the flow of current () from the positive () terminal to the negative () terminal. Without the flow of current, the heating effect cannot occur, and the bulb does not glow.
Problem 2:
What happens to a magnetic compass needle kept near a wire when the switch is turned 'ON'?
Solution:
The magnetic compass needle will show a deflection.
Explanation:
When the switch is 'ON', the circuit is closed and current () flows through the wire. This current creates a magnetic field around the wire (Magnetic Effect of Current), which exerts a force on the compass needle, causing it to move from its North-South alignment.