Current Electricity

Six similar bulbs are connected as shown in the figure with a DC source of emf E, and zero internal resistance. The ratio of power consumption by the bulbs when (i) all are glowing and (ii) in the situation when two from section A and one from section B are glowing, will be : [figure]

1. 4 : 9
2. 9 : 4
3. 1 : 2
4. 2 : 1

In the circuits shown below, the readings of voltmeters and the ammeters will be : [figure]

1. V1 = V2 and i1 = i2
2. V1 > V2 and i1 > i2
3. V1 > V2 and i1 = i2
4. V1 = V2 and i1 > i2

Which of the following acts as a circuit protection device?

1. inductor
2. conductor
3. switch
4. fuse

A set of n equal resistors, of value R each, are connected in series to a battery of emf E and internal resistance R. The current drawn is I. Now, the n resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10I. The value of n is

1. 10
2. 11
3. 20
4. 9

A battery consists of a variable number n of identical cells (having internal resistance r each) which are connected in series. The terminals of the battery are short-circuited and the current I is measured. Which of the graphs shows the correct relationship between I and n?

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

A carbon resistor of (47 4.7) k is to be marked with rings of different colours for its identification. The colour code sequence will be

1. Violet – Yellow – Orange – Silver
2. Yellow – Violet – Orange – Silver
3. Yellow – Green – Violet – Gold
4. Green – Orange – Violet – Gold

The resistance of a wire is 'R' ohm. If it is melted and stretched to 'n' times its original length, its new resistance will be

1. Rn
2. n2R
3. Rn2
4. nR

A potentiometer is an accurate and versatile device to make electrical measurements of EMF because the method involves

1. potential gradients
2. a condition of no current flow through the galvanometer
3. a combination of cells, galvanometer and resistances
4. cells

A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf's is

1. 3 : 4
2. 3 : 2
3. 5 : 1
4. 5 : 4

The charge flowing through a resistance R varies with time t as Q = at - bt2, where a and b are positive constants. The total heat produced in R is

1. a3R2b
2. a3Rb
3. a3R6b
4. a3R3b