WBJEE: Important Questions and Preparation Tips – Electric Current

Students can’t miss any single topic of any subject if they want to get selected in WBJEE Examination 2018. But it is not possible for students to revise the complete theory before the examination. To tackle this problem students will have to make notes which should consists of all important concepts, formulae and previous year solved questions.

Electric Current is one of the important chapters in the syllabus of WBJEE entrance examinations. About 2-4 questions are being asked from this chapter in WBJEE examination. Find chapters notes of chapter Electric Current for WBJEE Entrance Examination 2018.

These notes include all important topics of chapter Electric Current like electric current, Ohm’s law, temperature dependence of resistivity, electrical energy, electrical power, combination of resistors, cell, emf, internal resistance, Kirchhoff’s rules, Wheatstone bridge, Meter Bridge etc.

Important Questions and Preparation Tips – Electrostatics

Important Concepts:

Some previous years solved questions are given below:

Question 1:

A galvanometer having internal resistance 10Ω requires 0.01 A for a full scale defection. To convert this galvanometer to a voltmeter of full-scale deflection at 120V, we need to connect a resistance of

(A) 11990 Ω in series

(B) 11990 Ω in parallel

(C) 12010 Ω in series

(D) 12010 Ω in parallel

Solution 1:

We have,

V = 120

I_g = 0.01 A

Hence, the correct option is (A).

Important Questions and Preparation Tips - Thermodynamics

Question 2:

Four cells, each of emf E and internal resistance r, are connected in series across an external resistance R. By mistake one of the cells is connected in reverse. Then the current in the external circuit is

Solution 2:

Hence, the correct option is (A).

Important Questions and Preparation Tips – Laws of Motion

Question 3:

A circuit consists of three batteries of emf E₁ = 1 V, E₂ = 2 V and E₃ = 3 V and internal resistances 1 Ω, 2 Ω and 1 Ω respectively which are connected in parallel as shown in the figure. The potential difference between points P and Q is

(A) 1.0 V

(B) 2.0 V

(C) 2.2 V

(D) 3.0 V

Solution 3:

The batteries are connected in parallel so, the effective resistance is given as:

So, the potential difference between two point P and Q = 2 Volt

Hence, the correct option is (B).

Important Questions and Preparation Tips – Work, Power and Energy

Question 4:

The current I in the circuit shown is

(A) 1.33 A

(B) Zero

(C)  2.00 A

(D) 1.00 A

Solution 4:

Hence, the correct option is (A).

Important Questions and Preparation Tips – Rotational Motion

Question 5:

Two cells A and B of e.m.f 2V and 1.5V respectively, are connected as shown in figure through an external resistance 10Ω. The internal resistance of each cell is 5 Ω. The potential difference E_A and E_B across the terminals of the cells A and B respectively are

Solution 5:

Let i be the current flowing through the circuit

On applying KVL,

Hence, the correct option is (C).

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