The work done in charging a capacitor to charge Q is stored as:
A. Chemical energy
B. Magnetic energy
C. Heat energy
D. Electrostatic potential energy
Answer: Option D
Solution (By JKSSB Mock Tests)
Work done to charge a capacitor is stored as electrostatic potential energy in the electric field between plates: U = ½QV = ½CV² = Q²/(2C). This energy can be recovered when capacitor discharges. Heat (A) is dissipated in resistance during charging, but ideal capacitor stores energy electrostatically. Memory aid: 'Capacitor energy = ½CV², stored in electric field'. This electrostatics concept is frequently tested in competitive exams. Always distinguish ideal capacitor (no resistance) from real circuits where some energy is lost as heat during charging.
Explanation:
SI base unit of thermodynamic temperature is kelvin (K). Celsius is derived unit, size 1°C = 1 K. Fahrenheit and Reaumur are other scales. Kelvin scale starts at absolute zero.
Explanation:
Q = mcΔθ = 2 × 4200 × 10 = 84,000 J = 84 kJ. Large specific heat of water makes it useful for cooling and climate moderation. Always check units: mass kg, c J/kg°C, ΔT °C.
Explanation:
A rocket works on the principle of conservation of linear momentum. As the exhaust gases are expelled downward at high velocity, they carry downward momentum. To conserve the total momentum of the system (which is initially zero), the rocket must acquire an equal and opposite (upward) momentum, propelling it forward.
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