Test: Electric Current & its Effects - Class 7 MCQ

A circuit breaker can be used over and over again. The basic circuit breaker consists of a simple switch, connected to an electromagnet.

Generally electrical current requires a close path or circuit to flow, so when switch is off it won't flow. A switch prevents or allow the current to flow through it.

The correct answer is C: It opens or closes the circuit.
- A switch in an electric circuit is a device used to control the flow of electricity.
- When the switch is closed, it completes the circuit, allowing electric current to flow.
- When the switch is open, it breaks the circuit, stopping the flow of electricity.
- This functionality allows users to turn electrical devices on and off.

An electric fuse is a safety device used to prevent electrical circuits from overheating and causing fires. It acts like a barrier that breaks the circuit if the current exceeds a safe limit, protecting the wires and devices. 

• In the symbol of an electric cell, a longer line represents the positive terminal. This terminal is where the electric current flows out of the cell. Just like a plus sign (+) means addition, the longer line in the symbol of an electric cell shows the positive side where electricity comes out.

When two cells are joined together via connecting wires in such a way that the positive end of one cell is joined the negative end of another cell. This arrangement is called a battery. Thus, a battery is a combination of two or more cells.

An electromagnet is formed when electric current flows through a wire coil, generating a magnetic field. Unlike a permanent magnet, it can be turned on or off by controlling the current.

There is a thin filament present inside a bulb that glows and produces light. If filament of bulb gets broken, electric current will not flow through the bulb and it will not glow.

The correct answer is Iron. An electromagnet is a device consisting of a core of magnetic material surrounded by a coil, through which an electric current is passed to magnetize the core. An electromagnet is attracted by Iron. An electromagnet is used wherever controllable magnets are required.

Hans Christian Oersted was the first person to notice the deflection of compass needle every time the current was passed through the wire kept near it.