The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

tricky questions! need help! edexcel physics unit 2

Paper june 2013question 17 parts b) and especially d) any explanations?
Reply 1
Avatar for baro
baro
OP
Herearecthe questions
1433014395604-878764768.jpg249.0KB
Reply 2
Avatar for baro
baro
OP
And this one
14330143656371670570977.jpg256.2KB
Reply 3
Avatar for Avila.C
Avila.C
4
Original post by baro
Herearecthe questions


The resistance is lower, smaller current means the temperature is lower. There are fewer collisions taking place between the electrons with lattice ions, so less energy is dissipated.

This should be right, I hope? :smile:
it'd help if you included the whole question

but I think b) is about the effect of temperature on the resistance of metals (like bulb filaments)

the resistance of bulb filaments is a lot higher when they are glowing white hot than when they are not - e.g. if you measure the resistance of a filament bulb when the filament is at room temperature (using a low current from a dmm or similar) it will not correspond to the rated power and voltage printed on the bulb.
Reply 5
Avatar for Avila.C
Avila.C
4
Original post by baro
And this one


If the ammeter has resistance, the current decreases but doesn't affect the determination becausethe current through resistance (r) is measured. Or the resistance of the ammeter contributes to the total resistance. If the voltmeter has a smaller resistance it would draw the current measured not the current through resistance (r)
Reply 6
Avatar for baro
baro
OP
[QUOTE="Avila.C;56366155"]The resistance is lower, smaller current means the temperature is lower. There are fewer collisions taking place between the electrons with lattice ions, so less energy is dissipated.

This should be right, I hope? :smile:[/QUOTE yes thanks a lot :smile: but why is the resistance lower? From the equation V=IR if voltage is constant doesnt that mean resistance should actuallybe higher? Also, does " light up" in this context mean break up or as such?
Reply 7
Avatar for Avila.C
Avila.C
4
The resistance of an electrical component is a measure of its opposition to current. V = I R ---> R = I / V
The two main ways of increasing the current in an electrical circuit are by increasing the voltage or by decreasing the resistance. :smile:

I think 'Light up' is referring to the fact that the resistance is too high that there isn't enough current for the bulbs to turn on.
(edited 8 years ago)

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you