A rectangular gold bar has two sides of length 0.04 m and one side of length 0.1

Question

A rectangular gold bar has two sides of length 0.04 m and one side of length 0.10 m. To prevent theft, the block can be connected to a 1.90 V source across any opposite faces of the block. Find the current that can flow through the block along its longer side. The resistivity of gold is 2.44 times 10^-8 Ohm m. 1.23 times 106 A 3.17 times 106 A 7.78 times 106 A 1.46 times 107 A Resistance is futile. As the capacitor in the RC circuit above reaches its maximum charge, which of the following statements is FALSE: the voltage across the capacitor is at its maximum. the voltage across the resistor is zero. the sum of the voltages across the capacitor and resistor is equal to the initial voltage across the resistor. the sum of the voltages across the capacitor and resistor is equal to the initial voltage across the capacitor. A series RC circuit has a time constant of 2.0 s. The battery has a voltage of 50 V and the maximum current just after closing the switch is 1 A. The capacitor is initially uncharged. What is the charge on the capacitor 4.0 a after the switch is closed? 1.73 C 2.64 C 0.86 C 1.16 C 0.17 C

Explanation / Answer

(A)
V = I*R
I = V/R
Where,
R = (2.44*10-8*0.10)/(0.04*0.10)
R = 6.1*10^-7

I = 1.9/(6.1*10^-7)
I = 3.17 * 10^6 A
(B)
(a) True !!
(b) True !!
(c) True !!
(d) False !!

(C)
t = 2.0 s
We know, V = I*R
50 = 1 * R
R = 50
R*C = 2.0
C = 2/50 =  0.04 F

Max Charge, Q = C*v
Q = 0.04 * 50 = 2 C

Charge after 4.0 s,
q = Q* (1 - e^(-t/t)
q = 2 * (1 - e^(-4/2) )
q = 1.73 C

Correct option :- (a)

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