Electricity Test

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Electricity Test - 70

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Weekly Quiz Competition

Question 1
1 / -0

Choose the statement which is not correct in the case of an electric fuse.

A
Fuses are inserted in electric circuits of all buildings.

B
There is a maximum limit on the current which can safely flow through the electric circuits.

C
There is a minimum limit on the current which can safely flow in the electric circuits.

D
If a proper fuse is inserted in a circuit it will blow off if current exceeds the safe limit.

Solution

In case of electric fuse, there is only a maximum limit on the current which can safely flow in the electric circuits.
There is a minimum limit on the current which can safely flow in the electric circuits.
Question 2
1 / -0

Variation of current and voltage in a conductor has been shown in the diagram below. The resistance of the conductor is.

A
$$4$$ ohm

B
$$2$$ ohm

C
$$3$$ ohm

D
$$1$$ ohm

Solution

from ohm's law $$R=\dfrac VI$$
also, slope of given graph $$\dfrac VI$$
so $$R=$$ slope of graph
$$s=\dfrac{y_2-y_1}{x_2-x_1}$$

$$s=\dfrac{4-1}{4-1}=1$$
Resistance = 1 ohm
Question 3
1 / -0

Two wires of the same material are given. The first wire is twice as long as the second and has twice the diameter of the second. The resistance of the first will be.

A
Twice of the second

B
Half of the second

C
Equal of the second

D
Four times of the second

Solution

we know $$R=\rho l /A$$
so $$R\propto \dfrac{l}{r^2}$$
According to the question:
$$l_1=2l_2$$ and $$r_1=2r_2$$
so $$R_1=\dfrac{2}{2^2}R_2=\dfrac{1}{2}R_2$$
The resistance of the first will be Half of the second.
Question 4
1 / -0

Two resistors of resistance $$R_{1}$$ and $$R_{2}$$ having $$R_{1} > R_{2}$$ are connected in parallel. For equivalent resistance $$R$$ , the correct statement is

A
$$R > R_{1}+R_{2}$$

B
$$R_{1} < R < R_{2}$$

C
$$R_{2} < R < (R_{1}+R_{2})$$

D
$$R < R_{1}$$

Solution

For parallel combination:
$$\dfrac{1}{R_{Eq}}=$$$$\dfrac{1}{R_1}+$$$$\dfrac{1}{R_2}$$
Equivalent resistance of parallel resistors is always less than any of the member of the resistance system.
so $$R < R_{1}$$
Question 5
1 / -0

If three resistors of resistance $$2\Omega, 4\Omega$$ and $$5 \Omega$$ are connected in parallel then the total resistance of the combination will be

A
$$\dfrac{20}{19}\Omega$$

B
$$\dfrac{19}{20}\Omega$$

C
$$\dfrac{19}{10}\Omega$$

D
$$\dfrac{10}{19}\Omega$$

Solution

For parallel resistance connection we know that,
$$\dfrac{1}{R_{eq}}=\dfrac{1}{R_{1}}+\dfrac{1}{R_{2}}+\dfrac{1}{R_{3}}=\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{5}=\dfrac{19}{20}\Rightarrow R_{eq}=\dfrac{20}{19}\Omega$$
Question 6
1 / -0

Which of the following statement is false

A
Heat produced in a conductor is proportional to its resistance

B
Heat produced in a conductor is proportional to the square of the current

C
Heat produced in a conductor is proportional to charge

D
Heat produced in a conductor is proportional to the time for which current is passed

Solution

According to Joule's heating law - $$H = i^{2} Rt$$
We also know that current $$i = \dfrac{q}{t}$$.
Hence $$H = \dfrac{q^{2}R}{t}$$
$$\therefore H \propto q^{2}$$
Question 7
1 / -0

An electric heater kept in vacuum is heated continuously by passing electric current. Its temperature

A
Will go on rising with time

B
Will stop after sometime as it will lose heat to the surroundings by conduction

C
Will rise after sometime and there after will start falling

D
Will become constant after sometime because of loss of heat due to radiation

Solution

Unless the heat generation rate is matched by the rate of radiation, the temperature will continue to rise.

After that, the temperature will become constant.
Question 8
1 / -0

$$10$$ wires (same length, same area, same material) are connected in parallel and each has $$1\Omega$$ resistance, then the equivalent resistance will be

A
$$10\Omega$$

B
$$1\Omega$$

C
$$0.1\Omega$$

D
$$0.001\Omega$$

Solution

When $$n$$ no. of resistances are connected parallelly then

$$ \dfrac{1}{R_{eq} } = \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + \dfrac{1}{R} + ................$$

$$ \dfrac{1}{R_{eq} } = \frac{n}{R}$$

$$\Rightarrow$$ $$R_{eq} = \dfrac{R}{n}$$

$$\Rightarrow$$ $$R_{eq}=\dfrac {R}{n}=\dfrac {1}{10}=0.1\Omega$$
Question 9
1 / -0

A solenoid is at potential of difference $$60\ V$$ and current flows through it is $$15$$ ampere, then the resistance of coil will be

A
$$4\ \Omega$$

B
$$8\ \Omega$$

C
$$0.25\ \Omega$$

D
$$2\ \Omega$$

Solution

Given,
Potential difference $$V=60\ V$$
Current $$i=15\ A$$
Resistance $$R=?$$

Resistance $$=\dfrac {Potential\ difference}{Current}=\dfrac{60V}{15A}=4\Omega$$
Question 10
1 / -0

When 25 A current with 10 ohm resistance flowing per second then the power lost in the cable during transmission is

A
$$12.5 kW$$

B
$$6.25 kW$$

C
$$25 kW$$

D
$$3.15 kW$$

Solution

Power lost in cable $$= I^2R =10 \times (25)^{2} = 6250 W = 6.25 kW$$

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Electricity Test - 70

Result

Electricity Test - 70

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SHARING IS CARING

Question 1

Fuses are inserted in electric circuits of all buildings.

There is a maximum limit on the current which can safely flow through the electric circuits.

There is a minimum limit on the current which can safely flow in the electric circuits.

If a proper fuse is inserted in a circuit it will blow off if current exceeds the safe limit.

Solution

Question 2

$$4$$ ohm

$$2$$ ohm

$$3$$ ohm

$$1$$ ohm

Solution

Question 3

Twice of the second

Half of the second

Equal of the second

Four times of the second

Solution

Question 4

$$R > R_{1}+R_{2}$$

$$R_{1} < R < R_{2}$$

$$R_{2} < R < (R_{1}+R_{2})$$

$$R < R_{1}$$

Solution

Question 5

$$\dfrac{20}{19}\Omega$$

$$\dfrac{19}{20}\Omega$$

$$\dfrac{19}{10}\Omega$$

$$\dfrac{10}{19}\Omega$$

Solution

Question 6

Heat produced in a conductor is proportional to its resistance

Heat produced in a conductor is proportional to the square of the current

Heat produced in a conductor is proportional to charge

Heat produced in a conductor is proportional to the time for which current is passed

Solution

Question 7

Will go on rising with time

Will stop after sometime as it will lose heat to the surroundings by conduction

Will rise after sometime and there after will start falling

Will become constant after sometime because of loss of heat due to radiation

Solution

Question 8

$$10\Omega$$

$$1\Omega$$

$$0.1\Omega$$

$$0.001\Omega$$

Solution

Question 9

$$4\ \Omega$$

$$8\ \Omega$$

$$0.25\ \Omega$$

$$2\ \Omega$$

Solution

Question 10

$$12.5 kW$$

$$6.25 kW$$

$$25 kW$$

$$3.15 kW$$

Solution

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