ISC (Science) ISC Class 12 - CISCE Question Bank Solutions for Physics (Theory)

What type of transformer is used in a mobile phone charger?

Explain why core of a transformer is always laminated.

How will you convert a moving coil galvanometer into a voltmeter?

ε₁ and ε₂ are two batteries having emf of 34V and 10V respectively and internal resistance of 1Ω and 2Ω respectively. They are connected as shown in the figure below. Using Kirchhoff’s Laws of electrical networks, calculate the currents I₁ and I₂.

Why are the pole pieces of a horseshoe magnet in a moving coil galvanometer made cylinder in shape? 

On which conservation principle is Kirchoff's Second Law of electrical networks based?

A moving coil galvanometer has a coil of resistance 59 Ω. It shows a full-scale deflection for a current of 50 mA. How will you convert it to an ammeter having a range of 0 to 3A?

In the circuit shown in the figure below, E₁ and E₂ are two cells having emfs 2 V and 3 V respectively, and negligible internal resistance. Applying Kirchhoff’s laws of electrical networks, find the values of currents l₁ and I₂.

State how a moving coil galvanometer can be converted into an ammeter.

A moving coil galvanometer of resistance 55 Ω produces a full scale deflection for a current of 250 mA. How will you convert it into an ammeter with a range of 0 - 3A?

In the circuit shown in Figure below, E₁ and E₂ are batteries having emfs of 25V and 26V. They have an internal resistance of 1 Ω and 5 Ω respectively. Applying Kirchhoff’s laws of electrical networks, calculate the currents I₁ and I₂.

Assertion: When an electric current is passed through a moving coil galvanometer, its coil gets deflected.

Reason: A circular coil produces a uniform magnetic field around itself when an electric current is passed through it.

The figure below shows two batteries, E1 and E2, having emfs of 18V and 10V and internal resistances of 1 Ω and 2 Ω, respectively. W₁, W₂ and W₃ are uniform metallic wires AC, FD and BE having resistances of 8 Ω, 6 Ω and 10 Ω respectively. B and E are midpoints of the wires W₁ and W₂. Using Kirchhoff's laws of electrical circuits, calculate the current flowing in the wire W₃:

The figure below shows a circuit containing an ammeter A, a galvanometer G and a plug key K. When the key is closed:

A galvanometer of resistance 100 Ω gives a full-scale deflection for a potential difference of 200 mV.

1. What must be the resistance connected to convert the galvanometer into an ammeter of the range 0-200 mA?
2. Determine resistance of the ammeter.

With the help of a labelled diagram, show that the balancing condition of a Wheatstone bridge is

`R_1/R_2 = R_3/R_4` where the terms have their usual meaning.

Obtain the balancing  condition for the Wheatstone bridge arrangements as shown in Figure 4 below:

Write balancing condition of a Wheatstone bridge.

An I0m long uniform metallic wire having a resistance of 20Ω IS used as a  potentiometer wire. This wire is connected in series with another resistance of 480Ω
and a battery of emf 5V having negligible internal resistance. If an unknown emf e is balanced across 6m of the potentiometer wire, calculate

1) the potential gradient across the potentiometer wire

2) the value of the unknown emf e.

 A closed surface in vacuum encloses charges –q and +3q. The total electric flux emerging out of the surface is :