Current Electricity Test

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Current Electricity Test - 26

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Weekly Quiz Competition

Question 1
1 / -0

Kirchoff's first law, i.e., $$\sum i = 0$$ at a junction, deals with the conservation of

A
charge

B
energy

C
momentum

D
angular momentum

Solution

The principle of conservation of electric charge implies that: at any node (junction) in an electrical circuit , the sum of currents flowing into that node is equal to the sum of currents flowing out of that node. This is known as Kirchhoff's current law.
Question 2
1 / -0

In series combination of resistances:

A
p.d. is same across each resistance.

B
total resistance is reduced

C
current is same in each resistance

D
all above are true.

Solution

Components connected in series are connected along a single path, so the same current flows through all of the components. The current through each of the components is the same, and the voltage across the circuit is the sum of the voltages across each component. In a series circuit, every device must function for the circuit to be complete. One bulb burning out in a series circuit breaks the circuit. A circuit composed solely of components connected in series is known as a series circuit.
The total resistance of resistors in series is equal to the sum of their individual resistances. Hence, the Equivalent resistance is more than the individual resistances because a sum is taken of all the individual resistances. That is, $${ R }_{ total }={ R }_{ 1 }+{ R }_{ 2 }$$. The current is given as $$I={ I }_{ 1 }={ I }_{ 2 }$$.
Below is the diagrammatic representation of 2 resistors $${ R }_{ 1 }\quad and\quad { R }_{ 2 }$$ connected in series.
Question 3
1 / -0

What steady current can be drawn from an accumulator of capacity $$80\ Ah$$?

A
$$4\ A$$ for $$20\ hrs$$

B
$$40\ A$$ for $$6\ hrs$$

C
$$20\ A$$ for $$5\ hrs$$

D
$$2\ A$$ for $$100\ hrs$$

Solution

given capacity is 80Ah which is unit of charge accumulated. So either we can draw a 80A current for 1 hour or less current for longer time period.
$$I=\frac { dQ }{ dt } =\frac { Q }{ t } $$
for option A lets calculate total charge drawn from source -
$$Q=4A\times 20hr=80Ah$$
hence option A is correct.
Question 4
1 / -0

At temperature $$0 K,$$ the germanium behaves as a/an

A
conductor

B
insulator

C
super-conductor

D
ferromagnetic

Solution

0 K is a absolute zero, the electrons of the semi conductors are trapped and are immovable from their electron shell as they are in a low energy state. this makes the pure semiconductor an insulator. one must heat the semiconductor to give the enough energy to electrons to get free and to conduct electricity.So we can say At $$0 K,$$ there is no free charge carries in the germanium and hence it behaves as an insulator.
Question 5
1 / -0

Constantan wire is used for making standard resistance, because it has

A
high melting point.

B
low specific resistance.

C
high specific resistance.

D
negligible temperature coefficient of resistance.

Solution

Constantan is a copper-nickel alloy. Its main feature is its resistivity, which is constant over a wide range of temperatures. Thus it has low temperature coefficient of resistance.that's why it is used for making of standard resistances . Hence correct option is option D
Question 6
1 / -0

Which physical quantity cannot be determined with the help of potentiometer?

A
I

B
V

C
L

D
R

Solution

Potentiometer is a simple device used to measure the EMF, internal resistance of a cell. It consists of a board where a tungsten or manganese wire is fitted on it. It works on the principle that the potential dropped between two points in a wire of uniform cross section is directly proportional to the distance between the points. It can not measure the inductance L .
Question 7
1 / -0

Two non ideal batteries are connected in series. Consider the following statements
(A) The equivalent emf is larger than either of the two emfs.
(B) The equivalent internal resistance is smaller than either of the two internal resistances.

A
Both A and B are correct

B
A is correct but B is wrong

C
B is correct but A is wrong

D
Both A and B wrong

Solution

If we add two non ideal batteries in series then
so in case (a) the equivalent e.m.f. may be larger than either of two e.m.f., but in case (b) the equivalent e.m.f. may be smaller than either of two e.m.f.
In series total resistance is always greater than individual resistance, whether batteries are connected in any way
[i.e. either according to case (a) or case (b)].
Question 8
1 / -0

When potential difference is applied across an electrolyte, then Ohm's law is obeyed at

A
zero potential

B
very low potential

C
negative potential

D
high potential

Solution

When voltage is applied to an electrolyte, dissociation of ions starts.
At low voltages as the voltage increases the number of ions conducting also increases making a non linear increase of current.
After a certain voltage when the ions are dissociated and no more dissociation, the electrolyte behaves as a conductor and obeys ohm's law.
Thus at high voltages, an electrolyte obeys ohm's law.
Question 9
1 / -0

The smallest resistance that can be obtained by the combination of $$n$$ resistors, each of resistance $$R$$ is:

A
$$n^2R$$

B
$$nR$$

C
$$\dfrac{R}{n^2}$$

D
$$\dfrac{R}{n}$$

Solution

For smallest resistance, the resistors are to be connected in parallel. The effective resistance $$= $$ R/n.
Question 10
1 / -0

Potentiometer measures potential more accurately because

A
it measures potential in open circuit.

B
it uses sensitive galvanometer for null deflection.

C
it uses high resistance potentiometer wire.

D
it measures potential in closed circuit.

Solution

Potentiometer measures the emf of a cell when no current flows through its galvanometer, following the laws of wheatstone bridge. Since the circuit is open(no current in balanced state), the accuracy of the measurement is more as compared to the other methods.

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Current Electricity Test - 26

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Current Electricity Test - 26

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SHARING IS CARING

Question 1

charge

energy

momentum

angular momentum

Solution

Question 2

p.d. is same across each resistance.

total resistance is reduced

current is same in each resistance

all above are true.

Solution

Question 3

$$4\ A$$ for $$20\ hrs$$

$$40\ A$$ for $$6\ hrs$$

$$20\ A$$ for $$5\ hrs$$

$$2\ A$$ for $$100\ hrs$$

Solution

Question 4

conductor

insulator

super-conductor

ferromagnetic

Solution

Question 5

high melting point.

low specific resistance.

high specific resistance.

negligible temperature coefficient of resistance.

Solution

Question 6

I

V

L

R

Solution

Question 7

Both A and B are correct

A is correct but B is wrong

B is correct but A is wrong

Both A and B wrong

Solution

Question 8

zero potential

very low potential

negative potential

high potential

Solution

Question 9

$$n^2R$$

$$nR$$

$$\dfrac{R}{n^2}$$

$$\dfrac{R}{n}$$

Solution

Question 10

it measures potential in open circuit.

it uses sensitive galvanometer for null deflection.

it uses high resistance potentiometer wire.

it measures potential in closed circuit.

Solution

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