Electric Charge and Electric Current - UNSOLVED PRACTICE SET

Q7. Define electric current. Write its formula, SI unit, and state whether it is a scalar or vector quantity.

Q8. What is the charge on one electron? How many electrons make up 1 coulomb of charge? (Charge of 1 electron = 1.6 × 10⁻¹⁹ C)

Q9. Distinguish between conventional current and electron current. Why do we still use conventional current direction in circuit diagrams?

Q10. An electric bulb in a home circuit draws a current of 0.5 A. How much charge flows through it in 2 minutes? How many electrons does this represent?

Q11. How is an ammeter connected in an electric circuit? What properties should an ideal ammeter have? Why should it never be connected in parallel?

Q12. Explain the difference between a conductor and an insulator in terms of electric charge and free electrons. Give two Indian examples of each.

Q13. Explain the concept of electric charge and electric current in detail. Your answer must cover:
(a) what electric charge is and the two types of charges,
(b) the SI unit of charge and the charge on one electron,
(c) how current is defined as rate of flow of charge (I = Q/t),
(d) the difference between conventional current and electron flow, and
(e) why metals are good conductors and explain what happens to free electrons when a battery is connected.

Q14. Draw (or describe) a simple electric circuit consisting of a cell, switch, ammeter, and a bulb.
(a) Explain the role of each component.
(b) What happens to the current when the switch is open vs closed?
(c) If the cell provides a current of 0.8 A and the circuit runs for 5 minutes, calculate the total charge that flowed.
(d) How many electrons passed through the bulb in this time?
(e) Why does current flow from positive to negative terminal in the external circuit?

Q15. Explain the concept of electric charge with reference to atomic structure.
(a) What makes an object positively or negatively charged?
(b) State the law of conservation of charge.
(c) What is meant by the 'quantisation of charge'?
(d) How does charging by friction work — explain with the example of a plastic comb run through dry hair in Indian summers.
(e) Why do charged objects attract uncharged objects?

Q16. An electric geyser is rated 2000 W and runs on 220 V mains.
(a) Calculate the current drawn by the geyser (I = P/V).
(b) Calculate the charge flowing through it in 15 minutes.
(c) How many electrons pass through the geyser circuit per second?

Q17. In a torch, three cells each of EMF 1.5 V are connected in series. The torch bulb draws a current of 0.3 A.
(a) What is the total EMF of the battery?
(b) How much charge flows through the bulb in 10 minutes?
(c) If the torch runs for 4 hours continuously, what is the total charge delivered by the battery?
(d) State what happens to the brightness of the bulb as the battery discharges.

Q18. A conducting wire carries a current of 2.5 A.
(a) Calculate the charge flowing in 4 minutes.
(b) Find the number of electrons corresponding to this charge.
(c) If the current is doubled but time is halved, what is the new charge?
(d) In a parallel circuit, wire A carries 1.5 A and wire B carries 1.0 A. What is the total current from the source?