Test: Electrical Measuring Instruments - JEE MCQ

Sensitivity of the potentiometer means the smallest potential difference it can measure. It can be increased by reducing the potential gradient. The same is possible by increasing the length of the potentiometer. Hence the correct option is option C.

Changes(if required):
Solution:
We can use the formula E1/E2=L1/L2
E1=2v,E2=?,l1=30,l2=60
2/E2=30/60
E2=120/30=4v

For balanced Wheatstone bridge which is shown in figure a, P/Q​=S/R​
If we interchange the cell and galvanometer then circuit becomes as shown in figure b.
and balanced condition, P/S​=Q​/R⇒P/Q​=S/R​
Thus, balanced point remains unchanged.

Power, P= V₂/R​
R= V²/P​
R=220×220/100 ​=484Ω
The current flow in the circuit,
i= V′/R​ (V′= supplied voltage)
i=110/484​=0.2272A
The voltage drop across the bulb is 110V
The power consumed by the bulb,
P_b​=V²/R​=110×110​/484
P_b​=25W
The correct option is C.
 

The meter bridge principle is based on the Wheatstone bridge circuit which says that if at any point of(of a wire), the ratio of two resistances (say R1) is equal to the ratio of another two resistance (say R3 and R4 where R4is the unknown resistance),Then there shall be no flow of current at that point between those points and the edge containing the resistances (R1/R2 and R3/R4) therefore, applying it to the meter bridge, at such point, the galvanometer will show zero defection.

The bridge is said to be balanced when deflection in galvanometer is zero(I_g=0), i.e., no current flows through the galvanometer(branch BD).In the balanced condition,
P/Q=R/S
On mutually changing the position of the cell and galvanometer, this condition will not change.
 

 Wheat stone bridge follows

 P/R = Q/S

Bulb A,
P_A=100w
V_A=120v
We know that, P=VI
So, I=P/V=100w/120v=5/6A=0.83A
Bulb B,
P_B=100w
V_B=120v
We know that, P=VI
So, I=P/V=10w/120v=1/12A=0.083A
Bulb A will consume more energy than bulb B when they are connected in parallel.
 

When the variable resistor is adjusted, then the current in the galvanometer becomes zero, the ratio of two two unknown resistors is equal to the ratio of value of unknown resistance and adjusted value of variable resistance. By using a Wheatstone Bridge the unknown electrical resistance value can easily measure.

A wheatstone bridge is an electrical bridge consisting of two branches of a parallel circuit joined by a galvanometer and used for determining the value of an unknown resistance in one of the branches.