Physics
A student connects a bulb to a cell using two wires, but the bulb does not glow. On checking, the bulb is found to be in proper condition. On further inspection, a wire is found to be loose.
(a) Why did the bulb not glow even though it was not faulty?
(b) What is meant by a closed circuit?
(c) Why is electric current considered as a flow of charges?
(d) What is the conventional direction of electric current?
Answer
(a) The bulb did not glow because the circuit was incomplete (open circuit) due to the loose wire, so even though the bulb was fine, current could not flow without a continuous conducting path.
(b) A closed circuit is a complete and continuous path through which electric current can flow from the cell, through the components and back to the cell.
(c) Electric current is considered as a flow of charges because it is defined as the rate of flow of electric charge. In conductors, this charge is carried by electrons.
(d) The conventional direction of electric current is from the positive terminal to the negative terminal of a cell, opposite to the actual flow of electrons.
Related Questions
Assertion (A) : Current flows from body at higher potential to a body at lower potential.
Reason (R) : The direction of flow of electrons is from low potential body to a body at a higher potential.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
Assertion (A) : Longer wires have greater resistance and the smaller wires have lesser resistance.
Reason (R) : Resistance of a wire increases with increase in temperature.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
Two copper wires of equal length but different thickness are connected one by one to the same cell and bulb.
(a) In which wire will the rate of flow of the charge be greater? Give reason.
(b) Does a higher current mean that electrons move faster from the battery to the bulb?
(c) If current flows for a longer time, what happens to the charge passing per second? What happens to the total charge transferred?
Two identical bulbs are connected to different circuits. One bulb glows brighter than the other as it is connected to a cell of higher voltage.
(a) Why does the bulb connected to the higher voltage source glow brighter?
(b) What does potential difference represent?
(c) How does resistance affect electric current?
(d) Between a thin wire and a thick wire, which has greater resistance? Give reason.