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Lab 4 - Ohm's Law

# Lab 4 - Ohm's Law - PHY134 Classical Physics II Laboratory...

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PHY134 - Classical Physics II Laboratory Ohm's Law Current-Voltage Relationships and Resistance. In this experiment you will measure electric current as a function of voltage for two different resistors and for a light bulb. You will also measure the voltage and current for the two resistors connected in series and in parallel. A current vs. voltage plot is called the I-V characteristic of the device. Ohm's Law is satisfied when the I-V characteristic is a straight line. The resistance R is defined as the ratio of the applied voltage V and the resulting current I : R = V / I (Ohm's Law), (1) where V is expressed in Volts (V), the current in Amperes (A), and the unit for R is the Ohm ( =V/A). Equipment Power supply, Circuit board, Voltmeter, Ampere meter. Method The voltage across each device to be studied is varied by changing the output of a power supply (see Figure). Voltages and corresponding currents are measured by meters. CAUTION: Check your circuit to make sure it is correctly wired. Set your meters to their least sensitive ( i.e. highest number) scales before you turn on the power supply. Later you may (and should) switch to more sensitive setting as long as the meter is not overloaded. Procedure 1. Always turn the power supply down when building and modifying circuits. Connect the circuit as shown in Figure 1 with a resistor as the device under test. Start at low voltage and slow ly work your way up. Never exceed 10 Volts and 250 mA in this circuit. Space your voltage and current readings between 0 and these maxima.

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Mea sure the current read by the ammeter for at least 5 values of voltage between 0 and 10 Volts. Reverse the polarity of the power supply and the meters and repeat these
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Lab 4 - Ohm's Law - PHY134 Classical Physics II Laboratory...

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