Extech Instruments MT310 Instrukcja Użytkownika Pobierz pdf (Strona 3)

P31220 Lab

Experiment 1: Find the internal resistance of a Battery (15 minutes)

You have a 9V battery. Use the DMM to measure its voltage. There are two resistors on the

board. Measure their actual resistances using the DMM as an ohmmeter. You’ll need these

numbers later. Record your results on the Data Sheet. You can measure the resistance of the

diode if you want to, but you don’t have to.

Remember, an ammeter’s resistance is very small. We can’t measure current from a battery by

connecting an ammeter directly across its terminals. This would cause a large current to flow,

running down the battery very quickly and/or blowing the DMM’s internal fuse. We will

measure the internal resistance indirectly, by putting a resistor in series with our battery and

ammeter. Construct the following circuit:

Record your measurements and answer the Analysis Questions on the data sheet.

Experiment 2: Voltage Drops Across Series Resistors (15 minutes)

In Experiment 1, you might have observed that the measured voltage across the 240Ω resistor

was not exactly 9V. In this part of the lab, you will find out why. You have a plastic block with

a wire in it. Points a and e represent the two ends of the wire. Using a DMM as an ohmmeter,

measure the resistance between point a and the other four points on the wire, as well as the

actual resistance of the 27Ω resistor. Then construct the following circuit. Use the 6V power

supply instead of the battery. Measure the voltages between point a and the other four points

along the wire. In addition, measure the voltage across the 27Ω resistor and the voltage across

the power supply. Complete the data table and answer the Analysis Questions for Experiment 2.

Fig. 2: Circuit for Experiment 2

battery

240Ω

Fig. 2: Circuit for Experiment 1

Power

Supply

27Ω

a b c d e

Long Wire

Hint: 240Ω = red-yellow-brown

Hint: 27Ω = red-violet-black

1 2 3 4 5 6 7 8 ... 11 12

Brak uwag

Extech Instruments MT310 Instrukcja Użytkownika Strona 3