A gold wire has a resistivity of 2.44 times 10^-8 W middot m. If the wire is 5.7

Question

A gold wire has a resistivity of 2.44 times 10^-8 W middot m. If the wire is 5.73 m long with a diameter 0.840 mm and carries a current of 1.21 A, what is the resistance of this gold wire? a) 0.06 Ohm b) 2.5 times 10^-7 Ohm c) 6.3 times 10^8 Ohm d) 0.25 Ohm If you plug an electric toaster rated at 110 V into a 220-V outlet, current in the toaster will be a) twice what it should be b) the same as if it were plugged into 110V c) half what it should be d) more than twice what it should be. An electric appliance draw 1.5 amperes of current when it is 24-volt source. What is the resistance of this appliance? a) 0.063 Ohm b) 1.1 Ohm 16 Ohm d) 54 Ohm A light bulb is plugged into a 120-volt outlet and has a 0.7 A current in it. What is the power rating of the light bulb? a) 12 W b) 17 W c) 84 W d) 120 W A wire of resistance R dissipates power P when a current I passes through it. The wire is replaced by another wire with resistance 3R. The power dissipated by the new wire when the same current passes through it is a) P/9 b) P/3 c) 3P d) 6P

Explanation / Answer

22)

Resistance R = rho * l / A

a) R = rho * l /A

b) R = 2 * rho * l / A

c) R = rho * l / 2A

d) R = 2 * rho * l / 2A

least resistance is c)

23)

R = rho * l / A

R = (2.44 * 10^-4 * 5.73) / (pi * (0.84 * 10^-3)^2)

R = 630.72 ohm

24)

V = I * R

Answer is a) twice what it should be

25)

Resistance R = V / I

R = 24 / 1.5 = 16

Answer si c) 16 ohm

26)

power P = V * I

P = 120 * 0.7 = 84 W

Answer is c) 84 W

27)

power dissipation P = i^2 * R

if R = 3R then P = 3 P

Answer is c) 3P

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