Constructing experiment to prove P=IV

[PhysicsLearne]

Not sure if the title is clear enough, but basically I've got a practical in a couple of days time and I have to construct an experiment to prove that P=IV by proving that P is greatest when the value of r (internal resistance) is zero and total resistance is equal to R (normal resistance).

I'm quite confused at what this is actually asking me to to do. Any ideas.

thanks

 

[Bob S]

Is this a real project or a virtual project? One accurate way to measure power is to heat a resistor in a calorimeter, and measure the energy transferred to a cup of water. Suppose you had a 12-volt car battery with an internal resistance with about r = 1/100 ohm. Get a R=1 ohm resistor and put it in about a cup (about 225 cc) of water, and connect it to the battery. Get a thermometer and measure the rate at which the water heats up. P = I*V = V^2/R = 144 watts. Only about 1% of the battery power is lost in the internal resistance r.

 

[sir-pinski]

One possible approach to constructing an experiment to prove P=IV is to set up a simple circuit consisting of a power source (such as a battery), a resistor, and a voltmeter and ammeter to measure voltage and current, respectively.

First, record the voltage and current readings with the resistor connected in the circuit. Then, gradually decrease the value of the resistor (by using resistors of different values or by using a variable resistor) and record the corresponding voltage and current readings.

Next, plot a graph of voltage vs. current, with the x-axis representing current and the y-axis representing voltage. The slope of this graph will represent the resistance of the circuit, as resistance is equal to the change in voltage over the change in current (R=ΔV/ΔI).

According to Ohm's Law, V=IR, so the slope of the voltage vs. current graph should be equal to the resistance of the circuit.

To prove P=IV, you can then calculate the power (P=IV) for each combination of voltage and current readings and plot a second graph of power vs. current. The graph should show a linear relationship, with the slope representing the internal resistance (r) of the power source.

Finally, by manipulating the values of the resistor and measuring the corresponding power, you can show that the power is greatest when the internal resistance is zero and the total resistance is equal to the normal resistance (R). This will demonstrate that P=IV, as the power will be at its maximum when the voltage and current are at their maximum values.

In conclusion, by setting up a simple circuit and conducting various measurements and calculations, you can construct an experiment to prove P=IV and show the relationship between power, voltage, and current.