Govt. Exams
Entrance Exams
For balanced bridge: P/Q = R/S. Check: 10/15 = 20/30 → 2/3 = 2/3. The bridge is balanced, so no current flows through galvanometer (zero reading).
BCS theory explains superconductivity: below critical temperature, electrons form Cooper pairs with no scattering, resulting in zero resistance.
For infinite ladder: Rₑq = 1 + (Rₑq×1)/(Rₑq+1). Solving: Rₑq² - Rₑq - 1 = 0, giving Rₑq = (1+√5)/2 ≈ 1.618Ω (Golden ratio)
R = ρL/A. If L increases by 10% and volume constant, A decreases by ~9.1%. New R = 1.1R₀/0.91 ≈ 1.21R₀, so 21% increase.
With R = 0, by I = V/R, current becomes infinite. In practice, voltage source cannot be maintained across a superconductor
By Ohm's law in microscopic form: E = ρJ. Inside the conductor, electric field maintains the drift of electrons
Maximum power transfer theorem: Load resistance equals internal resistance. R = r = 2Ω for maximum power
In semiconductors, increased temperature promotes more electrons from valence to conduction band, increasing carrier concentration and decreasing resistance
By maximum power transfer theorem, maximum power is transferred to external load when load resistance equals internal resistance
Due to symmetry, current divides into three paths of 1Ω each in parallel at the first vertex, then similar distribution at other vertices. Equivalent = 1/3 + 1/6 + 1/3 = 5/6Ω
