DC Circuit-short Question and Answer

 TOPIC- DC Circuit -Short Question and Answer

Q.1.Why are domestic appliances connected in parallel?

Ans.The domestic appliances are connected in parallel due to the following reasons:

(i)The domestic appliance are rated for the same voltage (i.e.,230V) but different power. When

connected in parallel,the performance of each appliance become independent of the other.Thus a 230V, 250W TV receiver can be operated independently in parallel with a 230V,100W lamp.

(ii)If a break occurs in any one of the branch circuits,it will have no effect on the other branch circuit.

Q.2.Why does a cell posses internal resistance?

Ans.When current flows through a cell, it meets opposition from the electrodes and the electrolyte.

This opposition to current offered by the cell is called its internal resistance.

Q.3.Why is Wheatstone bridge method preferred to voltmeter-ammeter method for measuring resistance?

Ans.Wheatstone bridge method is preferred to voltmeter-ammeter method for measuring resistance due to the following reasons:

(i)The Wheatstone bridge method is independent of the fluctuations and variations in the supply voltage.

(ii)It removes the objectionable feature of voltage-ammeter method where the accuracy of measurement is limited by the accuracy of calibration of instruments.

Q.4.Why is Wheatstone circuit called a bridge?

Ans.The circuit is called a bridge because the galvanometer bridges the opposite junctions of the circuit.

Q.5.When the resistance connected in series with the cell is halved,the current is not exactly doubled but is slightly less.why?
 

Ans.This is owing to the internal resistance r of the cell.The current delivered by the cell is 

I= E/R+r When external resistance R is made R/2.the current will be slightly less than 2l.

Q.6.Is current a scalar or Vector?

Ans.Current is a scalar.It is because current at the junction in an electric circuit do not obey the laws of vector algebra.