# Confirming ohms law

It's never engaging when I hit the button to turn it on. L for a wire and to determine the resistivity for the material of which the wire is made. To become familiar with the voltmeter-ammeter method for measuring resistance. EQUIPMENT Board with ten 1-meter lengths of a wire mounted between binding posts, power supply, analog voltmetermultimeter used as ammeter and later as an ohmmeter, hook-up wire, micrometer.

Since the resistance R is constant, a plot of voltage V vs. Notice that resistance is always the ratio of Confirming ohms law across a device to the current through the device.

The two measures of V and i should, of course, be made simultaneously. Some further consideration of the voltmeter-ammeter method V-A method reveals that there is inherent error involved. Consider the two circuits cct. Thus, the V-reading is larger than that which is required so the calculated R would be in error i.

Thus, the measured current is larger than that which is required so the calculated R would be in error, i. Considering the role of internal meter resistance, cct. The Ohmmeter and Wheatstone Bridge provide two other methods for the determination of resistance. The ohmmeter is not generally a precision device but is adequate in many electronic applications.

The Wheatstone Bridge can be refined to provide precision resistance measures as might be required in the use of such as a resistance thermometer. A property of electrical resistance which may need to be considered in some cases is that it depends on temperature to some extent.

The resistance R is given by: Fortunately, is small for some metals such as copper and aluminum but can be relatively large for others. The latter are useful as resistance thermometers. One test of the resistivity law could be to measure the resistance R of various lengths L of a certain gauge diameter or cross-sectional area and kind material of wire.

A linear plot of R vs. If the diameter of the wire is measured, from which the area A of the wire may be calculated, then from the slope of R vs.

L, could be found. Bear in mind that the colors of the lead wires in this experiment will differ from the colors of the probes in the precautions. Adjust the power supply to zero volts and connect the circuit as shown below leaving the voltmeter probe P disconnected at this time.

Set the ammeter on DCA function and on the 10 A range. Set the voltmeter on DCV function and use the 15V range. Turn the power supply on and slowly increase the voltage until A and V begin to show readings. It is now a matter of reading A and V simultaneously to provide data for the V vs. The range for i should be from about 0.

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Give some thought to the criteria involved and choose the current increments to provide an appropriate number and distribution of points. Record this V vs. In attempting to read voltage and current simultaneously, perhaps two partners could each read a meter on some signal.

Resistivity Law Adjust the power supply to zero volts and remove the probe from the terminals. Increase the power supply voltage until the current through the wire is about 0. After a few minutes, when thermal equilibrium is reached, the current should stabilize.

Touch the probe to the lm terminal and read and record voltage and current simultaneously. Continue this procedure until the 2m, 3m Use a Vernier micrometer to measure the diameter of the wire in several places. Do not stretch the wire in measuring the diameter.

Two measurements on each side-wire should be adequate. Also, close the micrometer, read it, and make a zero correction on subsequent readings.

A reliable average diameter is needed to ensure that the calculated area is representative of the wire. Ohmmeter Method Read the precautions for using a multimeter as an ohmmeter. Use the ohmmeter function of a multimeter to measure the resistance of the m length of wire.

To avoid possible damage to the meter, the wire must not be connected to the power supply when the ohmmeter is used.Any powered external speakers I connect to my laptop make a buzzing noise when my laptop is plugged in.

I also have battery-powered noise-canceling headphones that make the buzzing if noise canceli. Often referred to as the Ohm's law equation, this equation is a powerful predictor of the relationship between potential difference, current and resistance.

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Ohm's Law as a Predictor of Current. The Ohm's law equation can be rearranged and expressed as. Experiment Ohm’s Law 83 QUESTIONS 1. Read the information in the next column. How much current would it take to cause pain? What was the maximum current you measured for this experiment?

2. Why was there no danger to you while you per-formed this experiment? The current required for. Confirming Ohms Law Essay Ohms law V=i×R Hypothesis Volts equal amps multiplied by resistance. if voltages are kept constant and current is decreased and temperature is kept at a mere 15C and the circuits resistance will increase.

In the same way if resistance is increased current strength would decrease accordingly. The Voltage Transformer can be thought of as an electrical component rather than an electronic component. A transformer basically is very simple static (or stationary) electro-magnetic passive electrical device that works on the principle of Faraday’s law of induction by converting electrical energy from one value to another.

One of the biggest problems faced in analyzing electrical equipment is determining where the true problem is located. Fault Zone Analysis should be utilized to ensure that the actual problem is being detected and not just a secondary problem caused as a result of the real problem.

Senior Physics - Extended Experimental Investigations