Grade 7 - Electric current and its Effects

A fuse wire is a wire of-

• High resistivity and low melting point

• High resistivity and high melting point

• Low resistivity and low melting point

• Low resistivity and high melting point

When current is switched 'on' of a bulb it converts _______ energy into _______ energy.

• Electrical, heat

• Electrical, light

• Electrical, mechanical

• Electrical, sound

When current is switched on in an electric bell, it converts _______ energy into _______ energy.

• Electrical, light

• Electrical, sound

• Electrical, heat

• Mechanical, sound

Connection of more than one device/ appliance to a single socket is called-

• Overloading

• Short circuit

• Both

A common household device, that do not use an electromagnet in its working, is-

• The electric bell

• Geyser

• Telephone

• Loud speaker

The filament of A bulb, is a wire of

• High resistivity, low melting point

• Low resistivity, low melting point

• High resistivity, high melting point

• Low resistivity, high melting point

The heating coils/elements of different electrical appliances are usually made from ________ or ________ wires.

1. Copper 2. Aluminum 3. Nichrome 4. Tungsten

• 1 & 2

• 1 & 4

• 2 & 4

• 3 & 4

When electric current flows through the metal filament of the bulb it gets heated to very high temperature and becomes______ hot and start emitting _______.

• White, light

• Red, light

• White, heat

• Red, heat

Which one of the following is the most energy efficient

• LED

• Incandescent bulb

• CFL

The heating effect of an electric current is used in

• Hair dryer

• A fan

• A computer