Question

Some questions , I'll post in a second , please help:

Answer 1

Q1/ quantity of charge in coulombs passing though surface of area 2 cm^2 varies with time according to the equation q=4t^3+5t+6 where t is in seconds
a)what is the instantaneous current through the surface at t=1s
b)what is the value of current density

a) I did not know the answer :(
b)
I think we should use j=I/A

but I is missing I should get it from a) :(

Answer 2

Can't you even write the topic out instead of "help"?

P.S. that's just the same.

Answer 3

sorry :(

Answer 4

a) just plug in t=1 :)

Answer 5

Q2/ A 0.9 v potential difference maintained across a 1.5 m length of tungsten wire that has a cross sectional area of 0.6mm^2 what is the current in the wire ?

I think we should use I=V/R , but from where can I get R ?

Answer 6

Do you have the resistance of tungsten wire?

Answer 7

Can i get r from r/l = resistance of the element / 0.6*10^-6 ?

Answer 8

I can look it up , it doesn't matter but is my solution right ?

Answer 9

where did you get 0.6*10^-6?

Answer 10

Sorry * 10^-3

Answer 11

where did you get it?

Answer 12

Q4/ 10V battery is connected to a 120 ohmm resistor, neglecting the internal resistance of the battery calculate the power delivred to the resistor ?

Should I find the current first , =v/r and then use p=i^2 * r

or p=i *v ?

Answer 13

from mm^2 to m^2

Answer 14

Q4 doesn't have a question lol read it again

Answer 15

:D it says calculate the power that is delivered to the resistor

Answer 16

What are you given? (this is the guiding question lol)

Answer 17

Hey gave delta V also gave me the value of the resistor

Answer 18

V = 10v ,, R = 120 ohmm

Answer 19

So it's voltage and resistance? Use P=V^2/R :D

Answer 20

https://en.wikipedia.org/wiki/Electric_power

Answer 21

can I find the current first by I = V/R and then use P = I ^2 * R ?

Answer 22

ofc :)

Answer 23

In fact P=I^2R is derived from P=V^2/R :D

Answer 24

https://en.wikipedia.org/wiki/Electric_power

Answer 25

Ah man I hate this subject :( good thing it's the last time I'll study this subject :D

Thank you so much .

Answer 26

no problem :) good luck with your study onwards :D