# CBSE Class 10th Science 12 – Electricity MCQs

#### Watt hour is called as ____.

When a current of one ampere flows through a conductor at a potential difference of 1 V, it is also called as volt-ampere hour, because for one hour.

#### Electric current is defined as the rate of flow of ____.

Electric current is defined as the rate of flow of electric charge.

#### Conventional current flows from lower potential to higher potential.

The direction of conventional current is from higher potential to lower potential.

#### Electric current is measured in ____.

Electric current is measured in ampere.

#### Two bulbs A and B are connected in parallel across a cell. Resistance of the bulb A is R_{a} and resistance of the bulb B is R_{b}. The ratio of the currents in the bulb A to the bulb B is ____.

In parallel circuit the electric potential is same across all the resistors.
According to Ohm's law, electric potential difference across a resistor, v = iR.
As 'v' is same in both resistors, i_{a}/i_{b}=R_{b}/R_{a}
Hence, the ratio of the currents in the bulb A to the bulb B is R_{b} : R_{a}.

#### The resistance of a hot filament is less than the resistance of a cold filament.

When a bulb is glowing the temperature of the filament increases. The resistance of the filament of a bulb increases with increase in temperature. Hence, the resistance of hot filament is more than the resistance of cold filament.

#### In a closed electric circuit, the voltmeter should be connected in series in the circuit.

Voltmeter is used to measure voltage drop between two points in a circuit. In parallel combination potential difference will remain same across all the elements. Hence, in a closed electric circuit, the voltmeter should be connected in parallel with a circuit element to measure the voltage drop across it.

#### While a cell is being charged, ____ energy is converted into ____ energy.

While a cell is being charged, electrical energy is converted into chemical energy.

#### When 'n' identical resistors of resistance 'R' are connected in series, the resultant resistance is ____.

When 'n' identical resistors of resistance 'R' are connected in series, the resultant resistance is nR.

#### Two bulbs A and B are connected in series with a cell. Resistance of the bulb A is R_{a} and resistance of the bulb B is R_{b}. The ratio of the currents in the bulb A to the bulb B is ____.

In a series circuit there is only one pathway where charge can traverse. Hence, strength of electric current is same in all the resistors.

#### Terminal voltage is drawn from a cell when the circuit containing the cell is open.

Terminal voltage is drawn from a cell when the circuit containing the cell is a closed circuit.

#### Copper is not preferred to make fuse wire because it ____.

Copper has high melting point as it will not melt even on excessive heating. Because of this reason copper wire should not be used for making fuse wire.

#### The resistivity of a copper wire is infinitely large.

Copper is a good conductor of electricity. Hence, the resistivity of a copper wire is very small.

#### When 2 identical resistors of resistance 10 Ω are connected in parallel, the resultant resistance is ____ Ω.

When 'n' identical resistors of resistance 'R' are connected in parallel, the resultant resistance is R/n. Given, R = 10 Ω and n = 2 Hence, the resultant resistance is 5 Ω.

#### Resistance offered by the conductors does not depend on ____ of the conductor.

Resistance of a conductor depends on its length, area of cross-section and temperature. It does not depend on the surface area of the conductor.

#### If total charge 'Q' is flowing through a wire for a time of 't' seconds, then the current 'I' can be represented as ____.

Electric current is defined as the rate of flow of electric charge and is denoted by 'I'. Hence, I=Q/t

#### One horsepower (hp) is equivalent to ____.

Commercial unit of power is horsepower (hp). 1 horsepower is equal to 746 watt.

#### Ammeter is a device that is used to measure ____.

Ammeter is a device used to measure electric current.

#### The property of a body to oppose the flow of electric charge through it is called electric ____.

Electric resistance is the property of a body due to which it oppose or resist the flow of electric charge through it.

#### Two resistances of 6 Ω and 12 Ω are connected in parallel. Their net resistance is ____.

If R_{1} and R_{2} are the resistances connected in parallel and R is the net resistance of the combination, then
1/R = 1/R_{1} + 1/R_{2}
⇒ R= R_{1} × R_{2}/R_{1}+ R_{2}
⇒ R=6×12/6+12
⇒ R=72/18 = 4 Ω
Hence, the net resistance of the combination is 4 Ω.

#### The commercial unit of electric energy is ____.

The commercial unit of electric energy is kilowatt hour.

#### A parallel combination of resistors is used to obtain a ____.

When two or more resistors are connected in parallel, the net resistance of the combination is smaller than the least resistance in the combination. Hence, a parallel combination of resistors is preferred to obtain a smaller resistance with a given set of resistors.

#### Which of the following is the purpose of connecting a battery in an electric circuit?

Battery is the source of energy. It is used to maintain constant potential difference across the conductor.

#### A current is flowing through a wire. Then the nature of the wire is ____.

Current is the rate of flow of electrons through a wire. The total number of electrons are always equal to the number of protons, when current flows in a wire. Thus, the wire is electrically neutral.

#### If a man has ten 0.1 Ω resistors, then ____ is the smallest resistance he can obtain by using them.

To obtain the smallest resistance, all the resistors must be connected in parallel. When 'n' identical resistors of resistance 'R' are connected in parallel, the equivalent resistance, R'=R/n Given, n = 10 and R = 0.1 Ω R'=0.1/10 R' = 0.01 Ω Hence, the smallest resistance, the man can obtain by using a them is 0.01 Ω.

#### In a wire current flow is kept continuous by maintaining a potential difference between the ends of the wire.

A potential difference between the ends of a wire is produced by connecting the ends of the wire to a battery, which produces constant current in the wire.

#### Few resistors are connected in series to a battery and formed a closed electric circuit, then the current through each resistor in the closed electric circuit is same.

In series combination there is only one path for the flow of current as resistors are connected end to end. Hence, the same current flows through all the resistors in a series circuit.

#### A closed path through which charge continuously moves is known as closed circuit.

A closed path through which charge continuously moves is known as closed circuit.

#### According to Ohm's law, the electric current in a conductor is equal to the voltage across its ends.

Ohm's law states that, at a constant temperature, the electric current through a conductor is directly proportional to the potential difference across its ends.

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