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Basic Questions & Answers
Question 1:
What does an electric circuit mean?
Answer :
An electric circuit is the pathway in which current can flow. It consists of electric
devices, switching devices, source of electricity, etc. that are connected by
conducting wires.
Question 2:
Define the unit of current.
Answer :
The unit of electric current is ampere (A). When 1 C of charge flows through a
conductor in 1 s, it called 1 ampere (A) current.
I = Q/t
Question 3:
Calculate the number of electrons constituting one coulomb of charge.
Answer :
We know that one electron possesses a charge of 1.6 × 10^−19 C.
Number of electron = Total charge/Charge on 1 electron
= 1/1.6 × 10^-19= 6.25 × 10^18
So, the number of electrons constituting one coulomb of charge is 6 × 10^18
Question 4:
Name a device that helps to maintain a potential difference across a conductor.
Answer:
A cell, battery, power supply, etc. helps to maintain a potential difference across
a conductor.
Question 5:
What is meant by saying that the potential difference between two points is 1 V?
Answer :
When 1 J of work is required to move a charge of 1 C from one point to another,
then it is said that the potential difference between the two points is 1 V.
V =W/Q
1 V =1 J/1 C
Question 6:
How much energy is given to each coulomb of charge passing through a 6 V
battery?
Answer :
Potential Difference =Work done/Charge
or Work done (or Energy) = Potential Difference × Charge
So, Work done = 6 Volt × 1 Coulomb = 6 Joules
Question 6:
Why are coils of electric toasters and electric irons made of an alloy rather than a
pure metal?
Answer :
The resistivity of an alloy is higher than the pure metal and it does not corrode
easily. Moreover, even at high temperatures, the alloys do not melt readily.
Hence, the coils of heating appliances such as electric toasters and electric irons
are made of an alloy rather than a pure metal.
Question 7:
On what factors does the resistance of a conductor depend?
Answer :
The resistance of a conductor depends upon the following factors:
Length of the conductor
Cross-sectional area of the conductor
Material of the conductor
Temperature of the conductor.
Question 8:
What are the advantages of connecting electrical devices in parallel with the
battery instead of connecting them in series?
Answer :
In parallel there is no division of voltage among the appliances. The potential
difference across each appliance is equal to the supplied voltage and the total
effective resistance of the circuit can be reduced by connecting electrical
appliances in parallel.
Question 9:
What are the advantages of connecting electrical devices in parallel with the
battery instead of connecting them in series?
Answer :
In parallel there is no division of voltage among the appliances. The potential
difference across each appliance is equal to the supplied voltage and the total
effective resistance of the circuit can be reduced by connecting electrical
appliances in parallel.
Question 10:
Why does the cord of an electric heater not glow while the heating element does?
Answer :
The heating element of an electric heater is a resistor. According to Joule’s law
of heating, the amount of heat produced by it is proportional to its resistance.
H = I^2Rt
The resistance of the element of an electric heater is very high. As current flows
through the heating element, it becomes too hot and glows red. On the other hand,
the resistance of the cord is low. It does not become red when current flows
through it.
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