Which of the following has the highest specific heat capacity among common substances?
AIron
BWater
CCopper
DAluminum
Correct Answer:
B. Water
Explanation:
Water has specific heat capacity of 4186 J/(kg·°C), which is significantly higher than iron (~450), copper (~385), and aluminum (~900). This property makes water excellent for heat absorption and temperature regulation.
A wire of length L and cross-sectional area A has resistance R. If the wire is cut into two equal halves and connected in parallel, what is the new resistance?
AR/4
BR/2
CR
D4R
Correct Answer:
A. R/4
Explanation:
Each half has resistance R/2. When connected in parallel: 1/R_new = 1/(R/2) + 1/(R/2) = 4/R, so R_new = R/4.
Which statement about entropy is correct according to the Second Law of Thermodynamics?
AEntropy decreases in an isolated system
BEntropy of the universe always increases
CEntropy is conserved in all processes
DEntropy is independent of temperature
Correct Answer:
B. Entropy of the universe always increases
Explanation:
The Second Law of Thermodynamics states that for an isolated system, entropy always increases or remains constant, never decreases. This defines the direction of spontaneous processes and the arrow of time.
Which of the following exhibits wave-particle duality?
AOnly light
BOnly electrons
CBoth light and electrons
DOnly macro objects
Correct Answer:
C. Both light and electrons
Explanation:
De Broglie proposed that all matter exhibits wave-particle duality. Both light (photons) and electrons show properties of both waves and particles, confirmed by experiments like double-slit interference and photoelectric effect.