Current Electricity Test

Result

Current Electricity Test - 12

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Question 1
1 / -0

A potentiometer has a uniform wire of length 10m and resistance 5 ohms. The potentiometer is connected to an external battery of emf of 10V and negligible internal resistance and a resistance of 995 ohms in series. The potential gradient along the wire is:

A
1 mV/cm

B
5 mV/m

C
1 mV/m

D
5 mV/cm

Solution

The total resistance is the sum of the resistance of the potentiometer and the external resistance.
R = R_pot + R_ext = 5 + 995 = 1000 ohms .

The current through the potentiometer wire I = E/R = 10/1000 = 0.01AI = E/R = 10/1000 = 0.01A.

The potential drop across the potentiometer wire is
V = I × R_pot
⇒ V = 0.01 × 5
V = 0.05V

The potential gradient = (potential drop across the potentiometer wire)/ length of the potentiometer wire)
= 0.05/10
= 5 × 10⁻³V/m
= 5 mV/m
Question 2
1 / -0

In the measurement of resistance by a meter bridge, the current is necessarily reversed through the bridge wire to eliminate

A
End errors

B
Random errors

C
Index errors

D
Error due to thermoelectric effects

Solution

The connecting metal strips include a small resistance in the circuit called the end resistance.
On reversing the current, the end resistance tends to get canceled out.
Question 3
1 / -0

According to Ohm's law,

A
The electric current I flowing through a substance is proportional to the voltage V across its ends

B
The electric current I flowing through a substance is independent of the voltage V across its ends

C
The electric current I flowing through a substance is inversely proportional to the voltage V across its ends

D
The electric current I flowing through a substance is proportional to the square of voltage V across its ends

Solution

Ohm’s law states I is proportional to V. This holds good at steady temperatures and for the flow of constant current.
Question 4
1 / -0

Drift is the random motion of the charged particles within a conductor,

A
along with zero motion in the direction of the field

B
along with a decelerated motion in the direction of the field

C
along with a very slow net motion in the opposite direction of the field

D
along with accelerated motion in the direction of the field

Solution

The electrons in a conductor have random velocities and when an electric field is applied, they suffer repeated collisions and in the process move with a small average velocity, opposite to the direction of the field. This is equivalent to positive charge flowing in the direction of the field.