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Q89 (NDA-II/2008) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

DC current can be controlled by which one of the following components?

Result
Your answer: —  Â·  Correct: B
Explanation

Direct current (DC) can be controlled primarily by resistance. According to Ohm's law, the current through a resistor is inversely proportional to its resistance; thus, increasing resistance decreases the current for a given voltage [3]. In DC circuits, components like rheostats or variable resistors are specifically used to regulate current flow [3]. While impedance is a broader term that includes resistance and reactance, reactance (from capacitance and inductance) only opposes current in alternating current (AC) circuits [t1][t3]. In a steady-state DC circuit, a capacitor acts as an open circuit (infinite resistance) after charging, effectively blocking current rather than controlling it, and an inductor acts as a short circuit (zero resistance) [t1][t6]. Therefore, resistance is the fundamental component used for the active control and regulation of DC current [t4].

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192
  2. [3] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.6 RESISTANCE OF A SYSTEM OF RESISTORS > p. 181
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