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A Levels Physics (9702)•9702/12/O/N/24
Question 36 from 9702/12/O/N/24

Explanation

Kirchhoff's laws conserve charge and energy

Steps:

  • Kirchhoff's Current Law (KCL) states the algebraic sum of currents at a node is zero.
  • This reflects conservation of charge, as charge entering equals charge leaving.
  • Kirchhoff's Voltage Law (KVL) states the algebraic sum of voltages around a loop is zero.
  • This reflects conservation of energy, as work done by fields balances in a closed path.

Why A is correct:

  • KCL conserves charge (∑I = 0 at nodes), and KVL conserves energy (∑V = 0 in loops), per the laws' foundational principles.

Why the others are wrong:

  • B: Energy fits KVL, but current is not conserved; charge is.
  • C: Power is not conserved in either law; charge fits KCL but not first.
  • D: Resistance and power are not conserved quantities in Kirchhoff's laws.

Final answer: A

Topic: Kirchhoff's laws

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