Question
please answer these questions and show all work
1 Find total current lwing in the wire of circular cruss section with radius R if current density is given hy J = ao*r, where r is distance to the axis of the wire. 2 Find energy dissipated by resistor R=100 connected to the 10V battery in 3 minutes 3 A battery with 12 V emf and internal resistance r 1.0 is connected lo 1.0 k resistor. Find potential difference across the resistor. 4 Find equivalent resistance 6 5 a) Find resistance of aluminum wire of length 25 cm and cross section radius1 b) Assume a perfectly stretchable resistor with resistance R, length L and cruss section area A. Let's stretch our resistor to length 4L, what is its resistance now? c) Consider resistor from part a (aluminum wire). If initially it was at temperature 20 C (and resistance that you found in a), what is the resistance of the wire at 80C? For aluminurm resistivity = 2.65 * 10-nm and temperature coefficient = 0.00429 K-1
Explanation / Answer
As per guidlines i worked four problems
(2)
Q = i^2 Rt = V^2/R * t = (10 V)^2/100 * 3( 60 s) = 180 J
(3) 12 V
(4)3,9,6 ohm are connected in parallel
1/ R = 1/3 + 1/9 + 1/6
R = 1.63 ohm
1.63 ohm connceted series with 5 ohm so net reistance is
R' = 1.63 + 5 = 6.63 ohm
(5)
R = rho L/A = rho L/ pi r^2 = 2.65 * 10^-8 (0.25 m)/ pi (1* 10^-3 m)^2
=2.1 * 10^-3 ohm
