Class 10 Science Electricity Question and Answer

 

 Electricity

Q1 . What does an electric circuit mean?
 

Answer: A continuous conducting path consisting of wires and other resistances and a switch between the two terminals of a cell or a battery along which an electric current flows is called a circuit.

Q2 . Name a device that helps to maintain a potential difference across a conductor.
 

Answer: A battery.

Q3 . Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
 

Answer:  we know that resistance is inversely proportional to the area of the cross-section of the wire. So, the thicker the wire, the lower the resistance of the wire, and vice-versa. Therefore, current can flow more easily through a thick wire than a thin wire.

Q4 . Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it ?
 

Answer: According to Ohm’s law

V = IR
$\Rightarrow I=\frac{V}{R}...\left(1\right)$
Now, potential difference is decreased to half.
$\therefore$ New potential difference $V^{{}^{\prime }}=\frac{V}{2}$
Resistance remains constant.
So the new current, $I^{{}^{\prime }}=\frac{V^{{}^{\prime }}}{R}$
$=\frac{\left(\frac{V}{2}\right)}{R}$
$=\left(\frac{1}{2}\right)\left(\frac{V}{R}\right)$
$=\left(\frac{1}{2}\right)I=\frac{I}{2}$
Therefore, the amount of current flowing through the electrical component is reduced by half.

Q5 .  Judge the equivalent resistance when the following are connected in parallel :
(i) 1 Ω and 106 Ω,
(if) 1 Ω and 103 Ω and 106 Ω.
 

Answer: When the resistances are connected in parallel, the equivalent resistance is smaller than the smallest individual resistance.

(i) Equivalent resistance < 1 Ω.
(ii) Equivalent resistance < 1 Ω.

Q6 .  Why does the cord of an electric heater not glow while the heating element does ?
 

Answer: Heat generated in a circuit is given by I2R t. The heating element of the heater is made up of an alloy which has very high resistance. So, when current flows through the heating element, it becomes too hot and glows red due to the heating effect of the current. But the resistance of cord which is usually of copper or aluminum is very low so it does not glow.

Q7 .  What determines the rate at which energy is delivered by a current?
 

Answer: Resistance of the circuit determines the rate at which energy is delivered by a current.

Q8 .  How is a voltmeter connected in the circuit to measure the potential difference between two points ?
 

Answer: The voltmeter is always connected in parallel connection across the two points where the potential difference is to be measured in the circuit.

 

Q9 . Explain the following:

(i) Why is tungsten used almost exclusively for filament of electric lamps?
 

Answer: Tungsten is an alloy which has a very high melting point and very high resistivity so it does not burn or melt easily at a high temperature.

(ii) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal ?

Answer: The conductors of electric heating devices such as bread-toasters and electric irons, are made of an alloy rather than a pure metal because the resistivity of an alloy is much higher than that of pure metal and an alloy does not undergo oxidation (or burn) easily even at high temperature.

(iii) Why is the series arrangement not used for domestic circuits ?

Answer: The series arrangement is not used for domestic circuits  because :

• In a series connection, if one electrical appliance fails due to a flaw, all other electrical appliances fail as well.
• In a series connection, all electrical appliances share a single switch, making it impossible to turn them on and off independently.
• Because the electricity is split in a series connection, all of the appliances do not get the same voltage.
• In a series connection, the equivalent resistance becomes too much, resulting in a very tiny quantity of current flowing.

(v) Why are copper and aluminium wires usually employed for electricity transmission?

Answer: Copper and aluminium wires usually employed for electricity transmission

             (i) they have low resistivity.

            (ii) they are good conductor of electricity

    

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