a student investigates how the resistance of a piece of wire changes wit voltage across the wire.
the student connects an ammeter,voltmeter,battery,variable resistor and the wire in the electrical circuit.
question~~ the student keeps the tempreture of the wire constant during the investigation.
how does she do it?
- Steve4PhysicsLv 71 month ago
The temperature can't be kep perfectly constant. But temperature changes can be kept very small. The simplest approach is:
1) Take measurements quickly, with the power off just before and just after each measurement. Then the wire has little time to heat up.
2) Allow some time (e.g. a minute) between each measurement so the wire has time to return to room temperature.
3) Ensure the wire is straight and is not resting on a surface (i.e. wire is well ventilated); this allows any heat to be quickly lost which keeps the temperature-rise small.
4) Avoid large currents, since the heating power is proportional to current squared.
5) Take 2 sets of readings. First set with current increasing, second set with current decreasing. If they give the same (or very similar) results, this means heating has not affected results.
An additional approach is to embed the wire in a constant temperature environment, e.g. melting ice. But this may not be practical, depending on what facilities you have.