Current Electricity Test

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Current Electricity Test - 23

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Weekly Quiz Competition

Question 1
1 / -0

Choose the correct statement:

A
The potential difference between the terminals of a cell in closed circuit is called EMF of the cell.

B
Electromotive force and accelerating force have the same dimensions.

C
The internal resistance of an ideal cell is infinity.

D
The difference between the emf of a cell and potential difference across the ends of the cell is called lost volts.

Solution

When the battery is discharging, the terminals voltage of the battery is always $$\le$$ Emf of cell $$[\because r > 0]$$
$$\therefore $$ There will always be a difference which is defined to be lost volt.
Question 2
1 / -0

Four identical wires each having resistance $$R$$ are connected as shown in the figure. Equivalent resistance between A and B is:

A
$$\dfrac{R}{4}$$

B
$$\dfrac{R}{2}$$

C
$$4R$$

D
$$R$$

Solution

Simplified circuit is drawn. It is the series combination of the four resistances.

$$ R_{AB} = 4R$$
Question 3
1 / -0

The sensitivity of a potentiometer can be increased by
a) increasing the series resistance in the primary circuit
b) decreasing the length of the potentiometer wire
c) using a thin and high resistivity wire as a potentiometer wire
d) increasing the length of the wire

A
a and c are correct

B
b and d are correct

C
b and c are correct

D
a and d are correct

Solution

The sensitivity of potentiometer is inversely proportional to the potential gradient.
With increase in the series resistance the potential gradient of the wire decreases thereby helps us to measure the emf more accurately.
Increase in the length of the wire decrease the potential gradient of the wire thereby helps us to measure the emf more accurately.
Question 4
1 / -0

Wheatstones’s bridge cannot be used for measurement of very _______ resistances.

A
high

B
low

C
low(or) high

D
zero

Solution

From wheatstone bridge while measuring For resistances of very low value like few ohms , the effect of other components of the circuit like wires , galvanometer etc. might come into account. these components might introduce stray resistance to the calculation
.Therefore we cannot apply wheatstone bridge for low resistance.
Question 5
1 / -0

For a chosen non-zero value of voltage, there can be more than one value of current in:

A
Copper wire

B
Thermistor

C
nichrome wire

D
Manganine wire

Solution

Thermistor are made up of substance with high $$\alpha$$ , which is very much sensitive to temperature thereby a slight change in temperature varies its resistance with huge amount.
hence making more than one value of current possible for chosen non-zero value of voltage.
Question 6
1 / -0

According to international convention of colour coding in a wire

A
Live is red, neutral is yellow and earth is green

B
Live is red, neutral is green and earth is black

C
Live is brown, neutral is blue and earth is black

D
Live is red, neutral is black and earth is green

Solution

According to international color coding system in Old colors red is live ( or phase) black is neutral, green/ yellow is earth
and in New colors brown is live, blue is neutral and green/ yellow is earth.
Question 7
1 / -0

Specific resistance of a wire depends on the

A
Length of the wire

B
Area of cross-section of the wire

C
Resistance of the wire

D
Material of the wire

Solution

The resistivity or specific resistance of a material is an intensive property and depend only on material and temperature.
Question 8
1 / -0

A $$24 \ V$$ potential difference is applied across a parallel combination of four $$6 \ \Omega$$ resistor. The current in each resistor is:

A
$$1 \ A$$

B
$$4 \ A$$

C
$$16 \ A$$

D
$$36 \ A$$

Solution

Since the resistors are connected in parallel,the voltage across each resistor is the same ,i.e $$24 \ V$$.

Therefore, current in each resistor can now simply be calculated using the relation,

$$ I = \dfrac{V}{R} \implies I = \dfrac{24}{6.0} = 4.0 \ A $$
Question 9
1 / -0

If the emf of the cell in the primary circuit is doubled, with out changing the cell in the secondary circuit, the balancing length is

A
1) Doubled

B
2) Halved

C
3) Uncharged

D
4) Zero

Solution

When the emf in the primary circuit is doubled
$$ \Rightarrow $$ current is doubled

because $$ e = Irl$$

$$ I_{1}\times r lb = 2 I_{1}\times r_{1} lb^{1}$$

$$ \Rightarrow l^{1}b = \dfrac{lb}{2}$$

$$ \therefore $$ Balancing length is halfed.
Question 10
1 / -0

If the temperature of a conductor is increased, its resistance will

A
not increase.

B
increase.

C
decrease.

D
change according to the whether.

Solution

In a conductor , which already has a large number of free electrons flowing through it, the vibration of the atoms causes many collisions between the free electrons and the captive electrons. each collision uses up some energy from the free electron and is the basic cause of resistance.
the more the atoms jostle around in the material , the more collisions are caused and hence the greater the resistance to current flow.
now when temperature is increased Due to increase in thermo - electronic vibrations, the number of collisions are increased hence the resistance of conductors increase with rise in temperature.

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Current Electricity Test - 23

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Current Electricity Test - 23

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Question 1

The potential difference between the terminals of a cell in closed circuit is called EMF of the cell.

Electromotive force and accelerating force have the same dimensions.

The internal resistance of an ideal cell is infinity.

The difference between the emf of a cell and potential difference across the ends of the cell is called lost volts.

Solution

Question 2

$$\dfrac{R}{4}$$

$$\dfrac{R}{2}$$

$$4R$$

$$R$$

Solution

Question 3

a and c are correct

b and d are correct

b and c are correct

a and d are correct

Solution

Question 4

high

low

low(or) high

zero

Solution

Question 5

Copper wire

Thermistor

nichrome wire

Manganine wire

Solution

Question 6

Live is red, neutral is yellow and earth is green

Live is red, neutral is green and earth is black

Live is brown, neutral is blue and earth is black

Live is red, neutral is black and earth is green

Solution

Question 7

Length of the wire

Area of cross-section of the wire

Resistance of the wire

Material of the wire

Solution

Question 8

$$1 \ A$$

$$4 \ A$$

$$16 \ A$$

$$36 \ A$$

Solution

Question 9

1) Doubled

2) Halved

3) Uncharged

4) Zero

Solution

Question 10

not increase.

increase.

decrease.

change according to the whether.

Solution

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