If 25 W, 220 V and 100 W, 220 V bulbs are connected in series across a 440 V line, then

only 25 W bulb will fuse
only 100 W bulb will fuse
both bulbs will fuse
None of these

Solution

If specific resistance of a potentiometer wire is 10^–7 Ωm current flowing through it, is 0.1 amp and cross sectional area of wire is 10^–6 m², then potential gradient will be

10^–2 volt/m
10^–4 volt/m
10^–6 volt/m
10^–8 volt/m

Solution

Five resistances have been connected as shown in the figure. The effective resistance between A & B is

14/3 Ω
20/3 Ω
14 Ω
14 Ω

Solution

The wheat stone bridge is balanced, when P/Q = R/S, In the this case ³⁄₆=⁴⁄₈, so bridge is balanced & 7Ω resistance is not effective)

A heating coil is labelled 100 W, 220 V. The coil is cut in half and the two pieces are joined in parallel to the same source.The energy now liberated per second is

25 J
50 J
200 J
400 J

Solution

Power of heating coil = 100 W and voltage(V) = 220 volts. When the heating coil is cut into two equal parts and these parts are joined in parallel, then the resistance of the coil is reduced to one-fourth of the previous value. Therefore energy liberated per second becomes 4 times i.e., 4 × 100 = 400 J.

In the circuit shown in figure, the 5Ω resistance develops 20.00 cal/s due to the current flowing through it.The heat developed in 2 Ω resistance (in cal/s) is

23.8
14.2
11.9
7.1

Solution

Two 1000 W heaters when connected in parallel across 220 V supply produced heat Q_P in time t. If they are connected in series across the same power supply the heat produced in the same time is Q_S . What is Q_P/Q_S?

4
2
0.5
0.25

Solution

Three equal resistors connected across a source of e.m.f.together dissipate 10 watt of power. What will be the power dissipated in watt if the same resistors are connected in parallel across the same source of e.m.f.?

10/3
10
30
90

Solution

A leclanche cell supplies a current of one ampere for ten minutes. The electreochemical equivalent of hydrogen =0.00001014 gram per coulomb. The mass of hydrogen liberated is :

0.00625 g
0.01248 g
0.01872 g
0.02496 g

Solution

m = ZIt = 0.0000104 × 1 × 600 g

50 electric bulbs are connected in series across a 220 V supply and the illumination produced is I₁. 5 bulbs are fused. If the remaining 45 are again connected in series,the illumination produced is I₂. Which of the following is true ?

I₁ = I₂
I₁< I₂
I₁> I₂
It will depend on the resistance of each bulb.

Solution

Resistance of 45 bulbs in series is less than that of 50 bulbs. Since illumination is proportional to the heat produced (^V²t⁄_R), therefore it will be more with 45 bulbs.

In the Seebeck series Bi occurs first followed by Cu and Feamong other. The Sb is thelastin the series. If ξ1 be thethermo emf at the given temperature difference for Bi – Sb thermocouple and ξ, be that for Cu-Fe thermocouple, which of the following is true?

ξ₁ = ξ₂
ξ₁ < ξ₂
ξ₁ > ξ₂
Data is not sufficient to predict it.

UnAttempted

0

Attempted

0

Correct

0

Wrong

0

Complete