HELP! phys prac on wed (1 Viewer)

[Jenn]

This is my phys prac.. any one can help me?
hehe
Task: when a lamp is dissipating a greater power, the temperature increases and hence the resistance of the filament changes. you are to investigate how the power (P) dissipated by the filament of a lamp varies with the resistance (R) of the filament by using a circuit diagram ( circuit diagram was included which has a power supply, rheostat, ammeter, voltmeter and lamp)
btw... to get a straight line graph,.. what do we plot against what...
is it P against R and or P against V or what?
we just want a straight line that goes UP not DOWN....(positive inclination)
THANKS!!!

 

[-=«MÄLÅÇhïtÊ»=-]

You are asled "to investigate how the power (P) dissipated by the filament of a lamp varies with the resistance (R)"

So the axis are to be Power and Resistance.


u can use the equations V=IR and P=IV to work out the relationship between P and R

Current is controlled, T is variable
If T is constant, P=(I^2)R
I is constant, so the curve is linear, that looks like its gonna pass thru 0 (but u cant prove it going thru 0 in classroom prac)

As T increases, resistance increases (u are supposed to work this out in prac, I is changing)
Therefore the curve will bend because current is changing wrt temp.

Of course since this is a prac, it doesnt matter if u are right or wrong, all that matters is ur explanation.