Current Electricity

Two known resistances of R and 2R and one unknown resistance X are connected in a circuit as shown in the figure. If the equivalent resistance between points A and B in the circuit is X , then the value of X is . [figure]

1. 2( 3 - 1)R
2. R
3. ( 3 - 1)R
4. ( 3 + 1)R

The total length of potentiometer wire AB is 50 cm in the arrangement as shown in the figure. If P is the point where the galvanometer shows zero reading then the length AP is cm. [figure]

1. 25
2. 30
3. 15
4. 20

A battery with EMF E and internal resistance r is connected across a resistance R. The power consumption in R will be maximum when:

1. R = 2r
2. R = 2r
3. R = r2
4. R = r

A wire of resistance R is bent into a triangular pyramid as shown in figure with each segment having same length. The resistance between points A and B is R/n. The value of n is : [figure]

1. 16
2. 10
3. 12
4. 14

Current passing through a wire as function of time is given as I(t) = 0.02t + 0.01 A. The charge that will flow through the wire from t = 1 s to t = 2 s is

1. 0.02 C
2. 0.07 C
3. 0.06 C
4. 0.04 C

There are 'n' number of identical electric bulbs, each is designed to draw a power p independently from the mains supply. They are now joined in series across the mains supply. The total power drawn by the combination is :

1. np
2. p
3. pn2
4. pn

From the combination of resistors with resistance values R1 = R2 = R3 = 5 and R4 = 10 , which of the following combination is the best circuit to get an equivalent resistance of 6 ?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

A wire of length 25 m and cross-sectional area 5 mm2 having resistivity of 2 10-6 m is bent into a complete circle. The resistance between diametrically opposite points will be

1. 100
2. 2.5
3. 12.5
4. 50

In the figure shown below, a resistance of 150.4 is connected in series to an ammeter A of resistance 240 . A shunt resistance of 10 is connected in parallel with the ammeter. The reading of the ammeter is mA. [figure]

A motor operating on 100 V draws a current of 1 A. If the efficiency of the motor is 91.6\%, then the loss of power in units of cal/s is

1. 6.2
2. 2
3. 8.4
4. 4