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Q53 (NDA-II/2010) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

If a heater coil is cut into two equal parts and only one part is used in the heater, the heat generated will be

Result
Your answer: —  Â·  Correct: A
Explanation

The resistance (R) of a conductor is directly proportional to its length (l) [c1][c2]. When a heater coil is cut into two equal parts, the length of the wire is halved, which consequently halves the resistance of that part (R' = R/2) [t2][t3]. The heat generated (H) or power dissipated (P) by an electrical appliance connected to a constant voltage source (V) is given by the formula P = V²/R [t1][t7]. Since the voltage remains constant and the resistance is halved, the power becomes P' = V²/(R/2) = 2(V²/R) = 2P [t3][t5]. Therefore, the heat generated by using only one half of the coil will be doubled compared to the original coil [t5][t7]. This occurs because the decrease in resistance allows a higher current to flow, and at constant voltage, lower resistance leads to higher power consumption [t4].

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192
  2. [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Activity 11.3 > p. 178
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