Question

HELP PLEASE!!!

A metal wire carries a current of 100 mA. How long does it take for 2 x 1020 electrons to pass a given cross-section of the wire?

3.2 s

32 s

320 s

200 s

Answer 1

For the first one 320

second

1200W

Data

R = 12 Ω ∆V = 120V I =? P =?

Solution:

According to Ohm’s law,

∆V = I R

I = ∆V / R  

= 120 / 12  

= 10 A

Power P = I ∆V  

= 10 x 120  

= 1200 W

Third

∆V = 120 V P = 60 W I =? R =?

Use the formula, P = I ∆V

I = P / ∆V = 60 / 120 = 0.5 A

∆V = I R

R = ∆V / I = 120 / 0.5 = 240 Ω