Current Electricity Test

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Current Electricity Test - 29

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Weekly Quiz Competition

Question 1
1 / -0

What is the driving force in a working Electrical Circuit?

A
Voltage Difference

B
Current

C
Temperature difference

D
Chemical Imbalance

Solution

When a potential difference is applied across a resistor then randomly moving free electrons start to move towards positive terminal due to force applied by electric field generated due to voltage difference . thus a start to Current Flows from High Voltage to Low Voltage.
Voltage is cause and current is effect.Hence correct option is A.
Question 2
1 / -0

The effective resistance of a circuit containing resistances in parallel is.

A
equal to the sum of the individual resistances.

B
smaller than any of the individual resistances.

C
greater than any of the individual resistances.

D
sometimes greater and sometimes smaller than the individual resistances.

Solution

The effective resistance of a circuit containing resistances in parallel is smaller than any of the individual resistances.
For example : $R_1 = 2\Omega$ and $R_2 = 3\Omega$
$\therefore$ Effective resistance $\dfrac{1}{R_p} = \dfrac{1}{R_1}+\dfrac{1}{R_2}$
OR $\dfrac{1}{R_p} = \dfrac{1}{2}+\dfrac{1}{3}$ $R_p = 1.2 \Omega < 2\Omega$
Question 3
1 / -0

The EMF of a cell can be defined as:

A
Work done in taking a unit positive charge once round the circuit

B
The open circuit voltage of the cell

C
The terminal voltage when the current is zero

D
All the above

Solution

EMF of cell can be defined as:
$\rightarrow$ Workdone in taking unit positive charge once round the circuit
$\rightarrow$ The open circuit voltage of cell
$\rightarrow$ The terminal voltage when current is zero
Question 4
1 / -0

The resistance of a semiconductor material (germanium or silicon) ________ with rise in temperature.

A
increases

B
decreases

C
remains the same

D
first increases then decreases

Solution

As the temperature rises, the valance band electrons in semiconductor jump into the conduction band due to gain in thermal energy and become capable of conducting current, thus increasing the conductance of semiconductor. Hence the resistance of semiconductor material decreases with increase in temperature.
Question 5
1 / -0

Specific resistance of all metals is mostly affected by

A
volume

B
pressure

C
temperature

D
magnetic field

Solution

Specific resistance of metal at temperature $T$ , $\rho_T = \rho_o(1+\alpha\Delta T)$
Specific resistance of metal depends on the temperature of the metal and it increases with increase in temperature. Also specific resistance of metals does not vary with volume of substance, pressure and applied magnetic field.
Question 6
1 / -0

In general, when the temperature of a conductor increases, its resistance

A
increases

B
decreases

C
remains the same with rise

D
first increases then decreases

Solution

With increase in temperature of conductor, the number of collisions between the free electrons increases due to increase in thermal energy resulting in the random motion of electrons. These electrons find it difficult to drift in a particular direction for conduction. Hence the resistance of conductor increases as the temperature increases.
Question 7
1 / -0

A man has five resistors each of value $\frac {1}{5}\Omega$ . What is the maximum resistance he can obtain by connecting them?

A
${1} \Omega$

B
$5 \Omega$

C
$\dfrac {1}{2} \Omega$

D
$\dfrac {2}{5} \Omega$

Solution

Maximum resistance is obtained when all the resistors are connected in series.
Effective resistance $R_{max} = R+R+R+R+R = 5R$
$\therefore$ $R_{max} = 5\times \dfrac{1}{5} =1\Omega$
Question 8
1 / -0

Given a current carrying wire of non-uniform cross-section. Which one of the following is constant through out the length of wire ?

A
Current only

B
Current and drift speed

C
Drift speed only

D
Current, electric field and drift speed

Solution

Current is uniform throughout the wire even if it is of non-uniform thickness. This is because charge passing through every cross sectional area per unit time remains the same throughout the wire. So, current remains the same.
Question 9
1 / -0

Calculate the current through a lamp of 25w operating at 220v.

A
2A

B
25A

C
0.114A

D
6A

Solution

Given : $P = 25$ W $V= 220$ volts
$\therefore$ Current through the lamp $I = \dfrac{P}{V} = \dfrac{25}{220} = 0.114$ A
Question 10
1 / -0

What is the series equivalent of $1000 \ \Omega$ resistor and $$2700 \ \Omega$$ resistor in series?

A
$2700 \ \Omega$

B
$3000 \ \Omega$

C
$3700 \ \Omega$

D
$1000 \ \Omega$

Solution

Given : $R_1 = 1000\Omega$ $R_2 = 2700\Omega$

Equivalent resistance in series combination is given by
$R_{eq} = R_1+R_2 = 1000+2700 = 3700$ $\Omega$

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Current Electricity Test - 29

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Current Electricity Test - 29

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Question 1

Voltage Difference

Current

Temperature difference

Chemical Imbalance

Solution

Question 2

equal to the sum of the individual resistances.

smaller than any of the individual resistances.

greater than any of the individual resistances.

sometimes greater and sometimes smaller than the individual resistances.

Solution

Question 3

Work done in taking a unit positive charge once round the circuit

The open circuit voltage of the cell

The terminal voltage when the current is zero

All the above

Solution

Question 4

increases

decreases

remains the same

first increases then decreases

Solution

Question 5

volume

pressure

temperature

magnetic field

Solution

Question 6

increases

decreases

remains the same with rise

first increases then decreases

Solution

Question 7

1Ω{1} \Omega 1Ω

5Ω5 \Omega 5Ω

12Ω\dfrac {1}{2} \Omega 21​Ω

25Ω\dfrac {2}{5} \Omega 52​Ω

Solution

Question 8

Current only

Current and drift speed

Drift speed only

Current, electric field and drift speed

Solution

Question 9

2A

25A

0.114A

6A

Solution

Question 10

2700 Ω2700 \ \Omega2700 Ω

3000 Ω3000 \ \Omega3000 Ω

3700 Ω3700 \ \Omega3700 Ω

1000 Ω1000 \ \Omega1000 Ω

Solution

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${1} \Omega$

$5 \Omega$

$\dfrac {1}{2} \Omega$

$\dfrac {2}{5} \Omega$

$2700 \ \Omega$

$3000 \ \Omega$

$3700 \ \Omega$

$1000 \ \Omega$