# Resistivity of a wire - AS coursework

1. Mar 2, 2006

### r0manticide17

Im to do an experiment tomorrow, but ive no idea what kind of readings to take! Im going to be using a 100mA ammeter, to measure voltage and current. The current is to stay constant more or less but im not sure what ranges of readings im to take. Anyone help me please?

2. Mar 2, 2006

### Chi Meson

To be clear, will you be using the Ammeter to measure the voltage?

And, is the point of the experiment to measure resistivity, not resistance?

3. Mar 2, 2006

### Staff: Mentor

To measure the resistance of something, you need to simultaneously measure the voltage across it and the current through it. You will need two meters for this. Are you going to buddy up in the lab?

4. Mar 2, 2006

### Chi Meson

An ammeter can be used as a voltmeter if used in conjunction with a resistor of known resistance (preferably large resisitance).

5. Mar 3, 2006

### Staff: Mentor

I know how to use a voltmeter and a resistor together as an ammeter, but I never thought about using an ammeter and resistor as a voltmeter. How does that work? Oh, I get it -- but the resistance of the ammeter degrades the accuracy of the measurement. I guess that's why you said to use a large value of external resistor....

6. Mar 6, 2006

### r0manticide17

thanks for all your replies, but the practical is now over with. Managed just fine, measured current and voltage, worked out resistance, and will be working out the resistivity of the wire soon enough