Class 12 Alternating Current worksheet

Sample questions

Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.

Section A · multiple choice

1. 1.

   The peak value of a 110 V (rms) supply is:

   1. 110/√2 V
   2. 110 V
   3. 220 V
   4. 110√2 V

   Answer

   (d) 110√2 V

   V₀ = √2 V_rms

2. 2.

   The reactance of a 18 × 10⁻² H inductor at an angular frequency of 950 rad/s is:

   1. 171 Ω
   2. 0.00585 Ω
   3. 342 Ω
   4. 17.1 Ω

   Answer

   (a) 171 Ω

   X_L = ωL

3. 3.

   The reactance of a 1 μF capacitor at an angular frequency of 800 rad/s is:

   1. 12,500 Ω
   2. 0.0008 Ω
   3. 625 Ω
   4. 1,250 Ω

   Answer

   (d) 1,250 Ω

   X_C = 1/(ωC)

Section B · short answer

1. 4.

   A 150 V (rms) supply drives a series circuit with R = 12 Ω, X_L = 58 Ω and X_C = 49 Ω. Find the current and the voltage across each element.

   Answer

   I = 10 A; V_R = 120 V, V_L = 580 V, V_C = 490 V

   Z = 15 Ω

2. 5.

   For a series circuit with R = 20 Ω, X_L = 30 Ω and X_C = 51 Ω across 290 V (rms), find the power factor and the average power.

   Answer

   20/29; 2,000 W

   P = V_rms I_rms cos φ = I²R

Section C · long answer

1. 6.

   A series LCR circuit has R = 80 Ω, X_L = 15 Ω and X_C = 99 Ω across a 464 V (rms) supply. Find the impedance, the current, the power factor, the average power and the voltage across each element.

   Answer

   Z = 116 Ω; I = 4 A; cos φ = 20/29; P = 1,280 W; V_R = 320 V, V_L = 60 V, V_C = 396 V

   Z = √(R² + (X_L − X_C)²)

Fresh sheets for your child

In the app, every Alternating Current sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.

Coming soon for Android and iPhone.

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