Current Electricity Quiz - ICSE Class 10 Physics

Free practice quiz: Current Electricity (ICSE Class 10 Physics). 50 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. A wire of resistance R is stretched to thrice its original length. What will be its new resistance?

   1. R/3
   2. 3R
   3. 9R
   4. R/9
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   Answer: C. 9R

   When a wire is stretched, its volume remains constant. Let the original length be L and the original cross-sectional area be A. The resistance R = ρ(L/A). When stretched to thrice its original length, the new length L' = 3L. Let the new cross-sectional area be A'. Since volume is constant, AL = A'L'. So, A' = AL/L' = AL/(3L) = A/3. The new resistance R' = ρ(L'/A') = ρ((3L)/(A/3)) = ρ(9L/A) = 9 * ρ(L/A) = 9R.

2. Which instrument is used to measure electric current?

   1. Voltmeter
   2. Ammeter
   3. Ohmmeter
   4. Galvanometer
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   Answer: B. Ammeter

   An ammeter is an instrument used to measure electric current in a circuit. It is always connected in series with the component through which the current is to be measured.

3. If the length of a conductor is doubled and its area of cross-section is also doubled, its resistance will:

   1. Remain unchanged
   2. Be doubled
   3. Be halved
   4. Be quadrupled
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   Answer: A. Remain unchanged

   The resistance of a conductor is given by R = ρ(L/A). If the length L is doubled (L' = 2L) and the cross-sectional area A is also doubled (A' = 2A), then the new resistance R' = ρ(L'/A') = ρ((2L)/(2A)) = ρ(L/A) = R. Thus, the resistance remains unchanged.

4. Which of the following is the correct combination for a voltmeter?

   1. High resistance, connected in series
   2. Low resistance, connected in series
   3. High resistance, connected in parallel
   4. Low resistance, connected in parallel
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   Answer: C. High resistance, connected in parallel

   A voltmeter is used to measure the potential difference across a component. To ensure that it draws negligible current from the circuit and does not significantly alter the voltage it is measuring, it must have a very high resistance. It is connected in parallel with the component across which the voltage is to be measured.

5. If a conductor carries a current of 1 Ampere and has a potential difference of 1 Volt across it, then its resistance is:

   1. 1 Ohm
   2. 1 Volt
   3. 1 Ampere
   4. 1 Watt
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   Answer: A. 1 Ohm

   According to Ohm's Law, R = V/I. If V = 1 Volt and I = 1 Ampere, then R = 1 V / 1 A = 1 Ohm (Ω).

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