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

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

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

1. equal to
2. less than
3. about 625 times
4. 200 times

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

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

1. free electrons
2. bound electrons
3. valence electrons
4. thermionic electrons

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

1. 625×10¹⁶ electrons
2. 6.25×10¹⁶ electrons
3. 62.5×10¹⁶ electrons
4. 0.625×10¹⁶ electrons

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

8) E.M.F in a circuit

1. increases circuit resistance
2. decreases circuit resistance
3. maintains potential difference
4. none of the above

9) Potential difference has the unit of

1. charge
2. energy
3. power
4. none

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

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

12) Electric current is a

1. scalar quantity
2. vector quantity
3. number only
4. none of the above

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

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

15) The specific resistance of a wire depends upon its

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