Extech Instruments MT310 Instrukcja Użytkownika Pobierz pdf (Strona 7)

P31220 Lab Name: ________________________________

Lab Section: ________________ T.A.’s ____________________________________________

Today’s Lab Partners: ___________________________________________________________

Ohm’s Law and DC Circuits

Data Sheets and Analysis Questions

Data and Analysis Questions for Experiment 1:

Actual resistance of the 240Ω resistor, measured with the DMM as an Ohmmeter: ________

Actual resistance of the 27Ω resistor, measured with the DMM as an Ohmmeter: ________

Actual voltage of the 9V battery: _________±_____

Voltage across the 240Ω resistor: V±δV: _________±_____

Current passing through the 240Ω resistor: A±δA: _________±_____

(To figure δV and δA, use 2% of the meter’s reading.)

1. The error in R is given by the resistor color code (silver = 10%, gold = 5%). Does V=IR ,

within error? (Hint: You may need to do a propagation of error calculation.) Please justify

your answer with an explanation, in addition to answering “yes” or “no”.

2. Although a battery is really one device, the circuit analysis is simplified if you treat it as a

pure voltage source in series with a pure resistance, called the “internal resistance.” The new

circuit is shown below. Everything inside the dashed line is inside the battery.

Recall that the voltmeter has nearly infinite resistance

compared to the other resistors in the circuit, and that the

ammeter’s resistance is so small that you can ignore it.

The resistance of this circuit is therefore (240Ω + r).

Calculate r, using Ohm’s Law (V=IR) and V = 9V.

Answer: _______________

240Ω

Fig. 5: Circuit for measuring

the internal resistance of a

battery.

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Extech Instruments MT310 Instrukcja Użytkownika Strona 7