The Electrical Equivalent of Heat InstructionsA Objective: To confirm Conservation of Energy with a thermal-electrical system Theory: We may not have yet covered the relationship for power in an electrical circuit: P = (AV) R - . If you have not seen this yet, a fuller discussion of power will be seen in chapter 26. Here's a short derivation: P = B _ AV 19 = (:)AV = IV. By Ohm's Law I = , so the equation for power can be written P = (AV) R We also recall the equation for the heat energy required to increase the temperature of a material is: Q = mcAT. Method: An immersion heater is essentially a resistor which generates thermal energy when an electric current passes through it, converting electrical energy into thermal energy in the liquid in which it is immersed. The power (rate of energy transformation) of a resistor can be found through P = . Knowing power and the time over which this process happens, we can find the electrical energy that is converted into thermal energy using P = . The thermal energy involved as water is heated can also be found by measuring its mass and temperature change: Q = mcAT. According to Conservation of Energy, these two energies should, within experimental limits, be the same. Procedure: 1. A multimeter - an electrical meter that can measure current, potential difference (voltage), and resistance, in both DC and AC circuits - is used to find the resistance and voltage in this experiment. The electrodes of the multimeter are placed through holes in the plug so a tight connection can be maintained. This gives a good electrical connection.2. Now we can take the resistance of the heater. which can be taken at the plug end. The actual heating element is covered with a silver-colored cover. This is to ensure that no one is shocked by the potential difference, but does not allow a measurement of the resistance at the heater itself. So we have to take the resistance measurement at the plug end. The copper of the wire has an extremely low resistance which can be ignored here. Record the resistance of the the heater. Note the small but visible decimal point. aw-$5. 3. The potential difference for our experiment is that of the public power supply. In the U.S.. this is 120V. but there is some small variation. Let's measure the potential difference ("voltage\") for our experiment today. Record this value 5.50 the mass of our sample of water without the cup is: 6. The initial temperature of the water Ean also be measured. 8. The nal temperature is taken. Record this temperature. 9. Calculate the amount of electrical energy generated in the heater using the values of the electrical quantities and the time measurement. 10. Calculate the amount of heat energy delivered to the water using the temperature increase and the water's specic heat and mass. 11. Compare the two energies using percent difference. 12. Question to Answer: If we had used a metal can instead of a styrofoam cup. how would the experiment be different? What additional issues would arise? 00:35.69 OLab Report - The Electrical Equivalent of Heat Name: Date: Objective: Data Tables AV R t E m(H,O) Ti Q % Diff