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COMEDK Current Electricity — practice questions — page 2

Explore 63 free Current Electricity questions in COMEDK 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 31–60 of 63.

A 12V battery (internal r = 0.5 Ω) drives current through 5.5 Ω external load. Find power dissipated in EXTERNAL resistor:Read the answer and worked solution →A copper wire of length 1 m and cross-section 1 mm² has resistivity 1.7 × 10⁻⁸ Ω·m. Its resistance is:Read the answer and worked solution →Two batteries with emf E₁ = 4V (r₁ = 1Ω) and E₂ = 6V (r₂ = 2Ω) in parallel. Find equivalent emf:Read the answer and worked solution →A wire of resistance 10 Ω is stretched to double its length without changing volume. Its new resistance:Read the answer and worked solution →Maximum power transfer from a source occurs when external resistance equals:Read the answer and worked solution →In a meter bridge experiment, the null point divides the wire as 30 cm and 70 cm. If known resistance is 6 Ω, the unknown is:Read the answer and worked solution →Merge equal resistors in seriesRead 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 →Tap every statement true of drift velocityRead the answer and worked solution →Complete the temperature coefficient definitionRead the answer and worked solution →Flip and pair: symbol with quantityRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Reading the definitions backRead the answer and worked solution →Property of the object or of the substance?Read the answer and worked solution →Order the chain: field to currentRead the answer and worked solution →

Worked practice questions

A 12V battery (internal r = 0.5 Ω) drives current through 5.5 Ω external load. Find power dissipated in EXTERNAL resistor:

  1. 11 W
  2. 22 W
  3. 24 W
  4. 8 W
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Correct answer: B. 22 W

Total R = 5.5 + 0.5 = 6 Ω. I = 12/6 = 2 A. Power in external = I² × R = 4 × 5.5 = 22 W.

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A copper wire of length 1 m and cross-section 1 mm² has resistivity 1.7 × 10⁻⁸ Ω·m. Its resistance is:

  1. 1.7 × 10⁻² Ω
  2. 1.7 × 10⁻⁵ Ω
  3. 1.7 × 10⁻⁸ Ω
  4. 17 Ω
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Correct answer: A. 1.7 × 10⁻² Ω

We have R = ρl/A. That is R = (1.7 × 10⁻⁸) × 1 / (1 × 10⁻⁶). That is R = 1.7 × 10⁻² Ω. So R = 0.017 Ω. (Convert mm² to m²: 1 mm² = 10⁻⁶ m².)

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Two batteries with emf E₁ = 4V (r₁ = 1Ω) and E₂ = 6V (r₂ = 2Ω) in parallel. Find equivalent emf:

  1. 3.33 V
  2. 10 V
  3. 4.67 V
  4. 5 V
Show answer and solution

Correct answer: C. 4.67 V

For parallel: E = (E₁/r₁ + E₂/r₂)/(1/r₁ + 1/r₂) = (4/1 + 6/2)/(1/1 + 1/2) = (4 + 3)/(1.5) = 7/1.5 ≈ 4.67 V.

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