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A wire of radius r has resistance R. If it is
stretched to a radius$\frac{\mathrm{r}}{2}$, its resistance will be :
1. 16 R 
2. 2 R
3. 4 R 
4. zero

A battery of e.m.f. 20 V and internal resistance
6$\mathrm{\Omega }$ is connected to a resistor as shown in figure.
If the current in the circuit is 1 amp, the resistance
of the resistor will be :

1. 14$\mathrm{\Omega }$
2. 16$\mathrm{\Omega }$
3. 28$\mathrm{\Omega }$
4. 7$\mathrm{\Omega }$ 

The value of current i in the circuit as shown in
figure is :

1. 1.8 A 
2. 0.8 A
3. 0.2 A 
4. 1.6 A

Electroplating is not provided to be used for
1. shinning appearance 
2. protection of metal against corrosion
3. fine finishing to the surface
4. hardening the metals

Two filaments of same length are connected first
in series then in parallel. For the same amount of
main current flowing, the ratio of the heat
produced is: 
1. 1 : 2 
2. 4 : 1
3. 1 : 4 
4. 2 : 1

Given a current carrying wire of non-uniform
cross-section. Which one of the following is
constant throughout the length of wire ?
1. current only
2. current and drift speed
3. drift speed only
4. current, electric field and drift speed

The current in the given circuit is

1. 0.3 amp 
2. 0.4 amp
3. 0.1 amp 
4. 0.2 amp
 

Same length of two identical wires are first
connected is series and then in parallel, then the
amount of heat produced in both the conditions
are in the ratio : 
1. 1 : 4 
2. 4 : 1
3. 3 : 1 
4. 1 : 2

The temperature of the cold junction of a thermocouple is 0°C and the temperature of the hot junction is T°C. The relation for the thermo emf is given by; $\mathrm{E}=\mathrm{AT}-\frac{1}{2}{\mathrm{BT}}^2$ (when A = 16 and B = 0.08). The temperature of inversion will be : 
1. 500°C 
2. 460°C
3. 600°C 
4. 400°C

The cell has an emf of 2V and the internal
resistance of this cell is 0.1W, it is connected to
a resistance of 3.9W. The voltage across the cell
will be : 
1. 1.95 V 
2. 1.5 V
3. 2 V 
4. 1.8 V

The internal resistance of a cell is the resistance of :
1. electrolyte used in the cell 
2. electrodes of the cell
3. vessel of the cell
4. none of these

An electric bulb marked 40 W and 200V, is used
in a circuit of supply voltage 100V. Now its power
is 
1. 10 W 
2. 20 W
3. 40 W 
4. 100 W

A wire of length L is drawn such that its diameter
is reduced to half of its original diameter. If the
initial resistance of the wire were 10 $\mathrm{\Omega }$, its new
resistance would be : 
1. 40 $\mathrm{\Omega }$ 
2. 80 $\mathrm{\Omega }$
3. 120 $\mathrm{\Omega }$ 
4. 160 $\mathrm{\Omega }$

Eels are able to generate current with biological
cells called electroplaques. The electroplaques
is an eel are arranged in 100 rows, each row
stretching horizontally along the body of the
fish containing 5000 electroplaques. The
arrangement is suggestively shown below. Each
electroplaque has an emf of 0.15 V and internal
resistance of 0.25 $\mathrm{\Omega }$. The water surrounding the
eel completes a circuit between the head and its
tail. If the water surrounding it has a resistance
of 500 $\mathrm{\Omega }$, the current an eel can produce in water
is about :

1. 1.5 A 
2. 3.0 A
3. 15 A 
4. 300 A

The cold junction of a thermocouple is
maintained at 10ºC. No thermo e.m.f. is
developed when the hot junction is maintained
at 530ºC. The neutral temperature is 
1. 260ºC 
2. 265ºC
3. 270ºC 
4. 520ºC

The equivalent resistance between A and B is

1. $\frac{8\mathrm{R}}{5}$
2. $\frac{5\mathrm{R}}{8}$
3. $\frac{3\mathrm{R}}{8}$
4. $\frac{3\mathrm{R}}{8}$

A potentiometer wire, 10 m long, has a resistance
of 40$\mathrm{\Omega }$. It is connected in series with a resistance
box and a 2 V storage cell. If the potential gradient
along the wire is 0.1 m V/cm, the resistance
unplugged in the box is 
1. 260 $\mathrm{\Omega }$ 
2. 760 $\mathrm{\Omega }$
3. 960 $\mathrm{\Omega }$ 
4. 1060 $\mathrm{\Omega }$

A current source drives a current in 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.
1. $\frac{{\mathrm{R}}_1{\mathrm{R}}_2}{{\mathrm{R}}_1+{\mathrm{R}}_2}$
2. ${\mathrm{R}}_1+{\mathrm{R}}_2$
3. zero
4. $\sqrt{{\mathrm{R}}_1{\mathrm{R}}_2}$

Two long conductors, separated by a distance d
carry current I₁ and I₂ in the same direction. They
exert a force F on each other. Now the current in
one of them is increased to two times and its
direction is reversed. The distance is also
increased to 3d. The new value of the force
between them is
1. $-\frac{2\mathrm{F}}{3}$
2. $\frac{\mathrm{F}}{3}$
3. -2F
4. $-\frac{\mathrm{F}}{3}$

Twelve resistors each of resistance 16 $\mathrm{\Omega }$ are
connected in the circuit as shown. The net
resistance between AB is

1. 1$\mathrm{\Omega }$
2. 2$\mathrm{\Omega }$
3. 3$\mathrm{\Omega }$
4. 4$\mathrm{\Omega }$

In the circuit shown, the current in the 1W
resistor is :

1. 0.13 A, from Q to P
2. 0.13 A, from P to Q
3. 1.3A from P to Q
4. 0A