You are given a resistance coil and a battery. In which of the following cases is largest amount of heat generated ?

When the coil is connected to the battery directly
When the coil is divided into two equal parts and both the parts are connected to the battery in parallel
When the coil is divided into four equal parts and all the four parts are connected to the battery in parallel
When only half the coil is connected to the battery

Solution

Silver and copper voltameters are connected in parallel with a battery of e.m.f 12 V. In 30 minute 1 g of silver and 1.8 g of copper are liberated. The energy supplied by the battery is[ ZAg = 11.2 × 10^–4gc^–1; ZCu = 6.6 × 10^–4 gc^–1]

720 J
2.41 J
24.12 J
4.34 × 10⁴ J

Solution

An electric heating element in vacuum is surrounded by acavity at constant temperature of 227ºC; it consumes 60W of power to maintain a temperature of 727ºC. What is the power consumed by the element to maintain a temperature of 1227º C?

101 W
304 W
90 W
320 W

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 watts if the same resistors are connected in parallel across the same source of e.m.f.?

10
¹⁰⁄₃
30
90

Solution

A current source drives a currentin a coil of resistance R₁ for a time t. The same source drives current in another coil of resistance R₂ for same time. If heat generated is same,find internal resistance of source.

\(\frac{R_{1}R_{2}}{R_{1}+R_{2}}\)
R₁+R₂
zero
\(\sqrt{R_{1}R_{2}}\)

Solution

Two different metals are joined end to end. One end is kept at constant temperature and other end is heated to a very high temperature. The graph depicting the thermo e.m.f.is

Solution

At the heighest point O

E = maximum and A shows temperature of inversion at which emf changes in sign.

The thermo e.m.f. of a thermocouple is 25μ V/ºC at room temperature. A galvanometer of 40 ohm resistance, capable of detecting current as low as 10^–5A,is connected with the thermocouple. The smallest temperature difference that can be detected by this system is

12ºC
0ºC
20ºC
16ºC

Solution

Two identical batteries, each of e.m.f.2 volt and internal resistance 1.0 ohm are available to produce heat in a resistance R = 0.5 Ω, by passing a current through it. The maximum power that can be developed across R using these batteries is

1.28 W
2.0 W
8/9 W
3.2 W

Solution

A wire of resistance 20 Ω is covered with ice and a voltage of 210 V is applied across the wire,then rate of melting theice is

0.85 g/s
1.92 g/s
6.56 g/s
All of these

Solution

Two bulbs of 500 W and 200W are manufactured to operate on 220 V line. The ratio of heat produced in 500 W and 200W, in two cases, when firstly they are connected in parallel and secondary in series will be

⁵⁄₂:²⁄₅
⁵⁄₂:⁵⁄₂
²⁄₅:⁵⁄₂
²⁄₅:²⁄₅

Solution

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