Chapter (10)

An electric bell is the use of the ____ effect of current.

• heating

• magnetic

• chemical

Answer explanation

Electric bell is constructed by using electromagnet.

The resistance of a/an _____ increases with increasing temperature.

• insulator

• conductor

• semiconductor

Answer explanation

Resistances of most conductors are found to increase with increasing temperature.

When an electric current flows through substance, it can produce ____ main effects.

• three

• two

• four

Answer explanation

Three main effects of electric current

1.heating effect

2.magnetic effect

3.chemical effect

An electric current is a flow of electric ______ from one place to another.

• power

• energy

• charge

Answer explanation

Current is flow of electrons, but current and electron flow in the opposite direction. Current flows from positive to negative and electron flows from negative to positive.

Conductors contain a large number of free _____.

• protons

• electrons

• photons

A circuit component which is made from a substance having resistance is called _______.

• inductor

• capacitor

• resistor

The _____ effect is used in electro-plating works.

• chemical

• heating

• magnetic

Answer explanation

Electroplating is the chemical process of applying a metal coating on another piece of metal (or another conductive surface) through an electro-deposition process.

The unit ampere is the unit of _____.

• water current

• electric current

• heat current

The resistance of _____ decreases with increasing temperature.

• carbon

• copper

• aluminium

Answer explanation

$R_t=R_0\left(1+\alpha t\right)$

where alpha is the temperature coefficient of resistivity.
The resistance generally increases with temperature. For small temperature changes the resistivity varies linearly with temperature.

Ohm’s law can be written as _____.

• P=VI

• Q=CV

• V=IR

Answer explanation

By Ohm’s law,

$V\propto I$
V=IR