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ISC Class 12 Current Electricity — practice questions

Explore 67 free Current Electricity questions in ISC Class 12 Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Current Electricity questions and exercises with answers

Showing questions 1–30 of 67.

A conductor carries a steady current when a charge of 30 C passes through a given cross-section in 1.5 minutes. The current in the conductor isRead the answer and worked solution →In a solid metallic conductor with no external electric field applied, the average velocity of the free electrons isRead the answer and worked solution →According to Ohm's law, the resistance R of a conductor is best described by which statement?Read the answer and worked solution →The resistivity $\rho$ of a conductor, appearing in $R = \rho l / A$, depends onRead the answer and worked solution →The relation between the electric field E inside a conductor and the current density j, written in terms of conductivity $\sigma$, isRead the answer and worked solution →The conductivity of a metal in the free-electron model is $\sigma = ne^2\tau/m$. The mobility $\mu$ of the charge carriers isRead the answer and worked solution →Materials are classified as conductors, semiconductors and insulators by resistivity. Metals fall in which range of resistivity?Read the answer and worked solution →How does the resistivity of a typical semiconductor change as its temperature is increased?Read the answer and worked solution →The power dissipated as heat in a resistor R carrying current I with voltage V across it can be written asRead the answer and worked solution →A heater rated to dissipate power P is run from a fixed supply. If its resistance R is halved (voltage unchanged), the power it dissipates becomesRead the answer and worked solution →A cell of emf $\varepsilon$ and internal resistance r is connected to an external resistance R. The current in the circuit isRead the answer and worked solution →Kirchhoff's junction rule, that the sum of currents entering a junction equals the sum leaving it, is a direct consequence ofRead the answer and worked solution →True or False: Current Electricity (ISC 12)Read the answer and worked solution →Match the Formula: Current Electricity (ISC 12)Read the answer and worked solution →True or false: what emf actually isRead the answer and worked solution →Complete the statement of Ohm's lawRead the answer and worked solution →Tap every way Ohm's law can failRead the answer and worked solution →Match each device or material to its behaviourRead the answer and worked solution →Sort each material by its resistivityRead the answer and worked solution →Complete the resistance relationRead the answer and worked solution →True or false: resistance and resistivityRead the answer and worked solution →Match each of Kirchhoff's rules to what it conservesRead the answer and worked solution →Kirchhoff's rulesRead the answer and worked solution →Order the steps: find an unknown resistance with a Wheatstone bridgeRead the answer and worked solution →True or false: internal resistanceRead the answer and worked solution →Which quantity is which?Read the answer and worked solution →Assertion and reasonRead the answer and worked solution →Charge carriersRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →

Worked practice questions

A conductor carries a steady current when a charge of 30 C passes through a given cross-section in 1.5 minutes. The current in the conductor is

  1. 0.20 A
  2. 0.33 A
  3. 20 A
  4. 45 A
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Correct answer: B. 0.33 A

1. For a steady current, $I = q/t$. 2. Convert time: $t = 1.5 \times 60 = 90\ \text{s}$. 3. $I = 30/90 = 0.33\ \text{A}$. 4. Option C (20 A) wrongly uses $t = 1.5\ \text{s}$; A divides further incorrectly. _Source: syllabus Physics Ch 3 "Current Electricity", p.1_

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In a solid metallic conductor with no external electric field applied, the average velocity of the free electrons is

  1. equal to the speed of light
  2. equal to the drift velocity
  3. directed along the field
  4. zero
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Correct answer: D. zero

1. With no field, electrons move only due to random thermal motion. 2. After each collision the direction of velocity is completely random. 3. The number moving in any direction equals the number in the opposite direction, so the vector average is zero. 4. Hence there is no net current; the answer is D. _Source: syllabus Physics Ch 3 "Current Electricity", p.2_

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According to Ohm's law, the resistance R of a conductor is best described by which statement?

  1. R is the slope of the I versus V graph
  2. R is the ratio V/I for the conductor
  3. R is the product of V and I
  4. R is independent of the material used
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Correct answer: B. R is the ratio V/I for the conductor

1. Ohm's law states $V \propto I$, written $V = RI$. 2. Rearranging gives $R = V/I$, the constant of proportionality. 3. R depends on both material and dimensions, so D is wrong. 4. R is the slope of V versus I (not I versus V), so A is wrong; C is dimensionally meaningless. _Source: syllabus Physics Ch 3 "Current Electricity", p.2_

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