1. The diameter of an atom is about
(i) 10-10 m
(ii) 10-8m
(iii) 10-2 m
(iv) 10-15 m
Answer: (i) 10-10 m
2. The number of compounds available in nature is
(i) 105
(ii) 300
(iii) 1000
(iv) unlimited
Answer: (iv) unlimited
3. The mass of a proton is …….. the mass of electron.
(i) equal to
(ii) less than
(iii) about 1837 times
(iv) 200 times
Answer: (iii) about 1837 times
4. The electrons in the last orbit of an atom arc called
(i) free electrons
(ii) bound electrons
(iii) valence electrons
(iv) thermionic electrons
Answer: (iii) valence electrons
5. If the number of valence electrons of an atom is less than 4, the substance is usually
(i) a conductor
(ii) an insulator
(iii) a semiconductor
(iv) none of the above
Answer: (i) a conductor
6. If the number of valence electrons of an atom is more than 4, the substance is usually
(i) a semiconductor
(ii) a conductor
(iii) an insulator
(iv) none of the above.
Answer: (iii) an insulator
7. If the number of valence electrons of an atom is 4, then the substance is usually
(i) a semiconductor
(ii) an insulator
(iii) a conductor
(iv) none of the above
Answer: (i) a semiconductor
8. One coulomb of charge is equal to the charge on
(i) 625 x 1016electrons
(ii) 6.25 x 1016electrons
(iii) 62.5 x 1016electrons
(iv) 0.625 x 1016 electrons
Answer: (i) 625 x 1016electrons
9. 1 cm3 of copper at room temperature has about
(i) 200 free electrons
(ii) 20 x 1010efree electrons
(iii) 8.5 x 1022 free electrons
(iv) 3 x 105free electrons
Answer: (iii) 8.5 x 1022 free electrons
10. The electric current is due to the flow of
(i) positive charges only
(ii) negative charges only
(iii) both positive and negative charges
(iv) neutral particles only
Answer: (iii) both positive and negative charges
11. E.M.F. in a circuit
(i) increases circuit resistance
(ii) decreases circuit resistance
(iii) maintains potential difference
(iv) none of the above
Answer: (iii) maintains potential difference
12. The electric current in a metallic conductor is due to the flow of
(i) electrons only
(ii) positive ions only
(iii) electrons and positive ions only
(iv) neutral atoms only
Answer: (i) electrons only
13. Potential difference has the unit of
(i) charge
(ii) power
(iii) energy
(iv) none of the above
Answer: (iii) energy
14. The electric current in a liquid is due to the flow of
(i) electrons only
(ii) positive ions only
(iii) negative and positive ions both
(iv) electrons and positive ions both
Answer: (iii) negative and positive ions both
15. Electric current is a
(i) scalar quantity
(ii) vector quantity
(iii) sometimes scalar and sometimes vector
(iv) number only
Answer: (i) scalar quantity
16. A billion electrons pass through a cross-section of a conductor in 10-3s. The current is
(1) 10-7A
(ii) 1.6×10-7A
(iii) 2 x 10-4A
(iv) 2.6 x 10-3A
Answer: (ii) 1.6×10-7A
17. The electric current in a discharge tube containing a gas is due to
(i) electrons only
(ii) positive ions only negative and positivc ions both
(iv) electrons and positive ions both
Answer: (iv) electrons and positive ions both
18. How long does it take 50 µC of charge to pass a point in a circuit if the current flow is 15mA?
(i) 3.33 x 10-31
(ii) 6 x 102s
(iii) 2 s
(iv) none of the above
Answer: (i) 3.33 x 10-31
19. The specific resistance of a wire depends upon
(i) its length
(ii) its cross-sectional area
(iii) its dimensions
(iv) its material
Answer: (iv) its material
20. The quantity of charge that will be transferred by a current flow of 10 A over 1 hour period is
(i) 10 C
(ii) 3.6 x 104 C
(iii) 2.4 x 102 C
(iv) 1.6 x 102 C