Thursday , October 18 2018
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# Electrical Basic Concept MCQs

1) The diameter of an atom is about:

1. 10-10 m
2. 10-02 m
3. 10-08 m
4. 10-15 m
EXPLANATION
No answer description required for this question.

2) 1 cm3 of copper at room temperature has about:

1. 200 free electrons
2. 20×1010 free electrons
3. 8.5×1022 free electrons
4. 3×1028 free electrons
EXPLANATION
No answer description required for this question.

3) The mass of a proton is ……………… the mass of electron.

1. equal to
2. less than
4. 200 times
EXPLANATION
No answer description required for this question.

4) If the number of valence electrons of an atom is 4, then the substance is usually a

1. conductor
2. insulator
3. semiconductor
4. none of the above
EXPLANATION
No answer description required for this question.

5) The electrons in the last orbit of an atom are called

1. free electrons
2. bound electrons
3. valence electrons
4. thermionic electrons
EXPLANATION
No answer description required for this question.

6) One coulomb of charge is equal to the charge on

1. 625×1016 electrons
2. 6.25×101electrons
3. 62.5×101electrons
4. 0.625×101electrons
EXPLANATION
No answer description required for this question.

7) The electric current is due to the flow of

1. positive charges only
2. negative charges only
3. both positive and negative charges
4. neutral particles only
EXPLANATION
No answer description required for this question.

8) E.M.F in a circuit

1. increases circuit resistance
2. decreases circuit resistance
3. maintains potential difference
4. none of the above
EXPLANATION
No answer description required for this question.

9) Potential difference has the unit of

1. charge
2. energy
3. power
4. none
EXPLANATION
No answer description required for this question.

10) The electric current in a liquid is due to the flow of

1. electrons only
2. protons only
3. negative and positive ions
4. electrons and positive ions
EXPLANATION
No answer description required for this question.

11) The electric current in a discharge tube containing a gas is due to

1. electrons only
2. positive ions only
3. positive and negative ions
4. electrons and positive ions
EXPLANATION
No answer description required for this question.

12) Electric current is a

1. scalar quantity
2. vector quantity
3. number only
4. none of the above
EXPLANATION
No answer description required for this question.

13) A billion electrons passes through a cross section of a conductor in 10-3 seconds. The current is

1. 1.6×10-7 A
2. 2×10-7 A
3. 10-7 A
4. 2.6×10-7 A
EXPLANATION
1 Billion = 1,000,000,000.00 Electrons

Here,

I = Q/T Q = 1,000,000,000.00×(1.60217662 × 10e-19) = 1.60217662 × 10e-10

I = 1.60217662 × 10e-10 × 10e-3

I = 1.6×10e-7

14) How long does it takes 50μC of charge to pass a point in a circuit if the current flow is 15 mA

1. 3.33×10-3 seconds
2. 6×10 seconds
3. 2 seconds
4. none of the above
EXPLANATION
Q = 50×10e-6

I = 15×10e-3

T = ?

Here

I = Q/T

or

T = Q/I

T = 50×10e-6/15×10e-3

T = 0.00333333333

T = 3.33×10e-3

15) The specific resistance of a wire depends upon its

1. length
2. cross sectional area
3. dimension
4. material