Current Electricity - Live Session (Nov)- NEET 2020Contact Number: 9667591930 / 8527521718

Page:

1.

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

2.

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$\mathrm{\Omega}$

3.

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

4.

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

5.

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

6.

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

7.

The current in the given circuit is

1. 0.3 amp

2. 0.4 amp

3. 0.1 amp

4. 0.2 amp

8.

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

9.

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

10.

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

11.

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

12.

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

13.

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 $\mathrm{\Omega}$

14.

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

15.

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

16.

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. $\frac{3\mathrm{R}}{8}$

17.

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 $\mathrm{\Omega}$

18.

A current source drives a current in a coil of

resistance R_{1} for a time t. The same source drives

current in another coil of resistance R_{2}

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. $\sqrt{{\mathrm{R}}_{1}{\mathrm{R}}_{2}}$

19.

Two long conductors, separated by a distance d

carry current I_{1} and I_{2} 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. $-\frac{\mathrm{F}}{3}$

20.

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$\mathrm{\Omega}$

21.

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

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