Electric Current & its Effects - Free MCQ Test with solutions, Class 7

An electric cell is depicted by a longer line for the positive terminal and a shorter, thicker line for the negative terminal in circuit diagrams.

A battery stores chemical energy and releases it as electrical energy, providing power to various devices in the circuit.

When electric current passes through the filament in an incandescent light bulb, the filament's electrical resistance causes it to heat up until it glows. This process produces visible light through a phenomenon known as incandescence.

This is why the filament:

• Becomes extremely hot
• Emits light when electricity flows through it

LED bulbs use electroluminescence to produce light without generating significant heat, unlike devices like hairdryers or toasters that use heating elements.

Miniature Circuit Breakers (MCBs) are increasingly preferred over traditional fuses for several reasons:

• Automatic Switching: MCBs automatically turn off when the current exceeds a safe limit, which helps prevent circuit overloads.
• Easy Reset: Unlike fuses that need replacement after blowing, MCBs can be easily reset to restore the circuit.
• Enhanced Safety: MCBs quickly disconnect power, reducing the risk of fires and damage to electrical circuits.
• Durability: MCBs generally have a longer lifespan than fuses, making them more reliable over time.

In summary, MCBs provide a safer, more convenient, and efficient alternative to traditional fuses.

A switch controls the flow of electric current by either opening (stopping current) or closing (allowing current to pass) the circuit.

The electric bell works on the magnetic effect of electric current, where an electromagnet pulls a metal strip to produce sound.

An ammeter is used to measure electric current in a circuit. It is connected in series with the components to measure the current flowing through them.

A coil of wire around an iron core that becomes magnetic when current flows through it is known as an electromagnet.

Plastic is an insulator and does not conduct electricity, unlike copper, aluminum, and iron, which are conductors.