13.2.3b - Resistivity Example

Resistivity example problem. From the Physics course by Derek Owens

[pardeepkumar-mvrw]

I ACCEPT YOU AS MY FAV TEACHER FOREVER! . AFTER LEARNING MANY THINGS FROM YOU.SIR

[derekowens]

@ummey786 That's a known constant for the material. You would get it by looking it up in a handbook, or in a textbook, or on Google.

[JoryRFerrell]

If you have a circuit or item (like an led), that needs 1 watt of power and 3.5v to operate. Dividing 1watt by 3.5v gives you 0.2857. This is the amps you need to run the led. But, say your battery put out more amps (but still at 3.5v) than that and the wire doesn't resist enough current. You need to add a resistor to cut down the amps to the correct amount. The voltage stays the same, but the current is dropped (resisted) to the desired level.

[SolBadguy]

you really teach better than my teacher. thank you!

[derekowens]

Yes, that's correct. We are actually dealing with an inequality in this case.

[NoPersonCreature]

Derek I get 3.36x10^-7 rather than -6 for the for the 1.68x10^-8 • 20.

[rvmixman]

Why is a resistor even necessary? I don't understand why circuits use them, especially in the case where the appliance wants low resistance?

[bonormayambem]

The question says your resistance must be less than 0.01ohm but in your solving, you made it such that the resistance was exactly 0.01... why?

[ummey]

where do u get the row value from???? which is 1.68x10^-8? plzz help

[thejdhingra]

when you are doing the calculations, 10^-8 reduces. why is that?

[atikilittezera]

What makes sure to use area of circle ?since there is no clue that wire is circular why we use A=pi×radius square? Please explain it for me

[Incci]

Derek i was checking the computations for the equations. It says thAt after solving for 3.36x10-8 (20m) / .1ohm it says that the exponent should have been -5 instead of -6. Can you please help me to clear it out if im wrong

thank you

[monasayed]

r= 1.037*10 -6 m2--r= 1.034*10 -3 m// r= 1.034 mm how he change that please any explenation

[rvmixman]

I know there's no resistor here, except by natural causes of the wires properties, but I thought I'd ask

[asafshalev]

if the distance is 20 meters away, wouldn't you need 40 meter of wire? Oo