5. In the lecture, I described Joule's use of an electric generator to heat a mass of water. Instead of a generator connected to a resistor, let there be a 12V battery connected to a 30 resistor. a) How much current will run through the circuit? b) If the heat generated by an electric circuit is given by: P = I²R how long would it take to raise 1 gallon of water by 1 degree celsius? (FYI, amps squared multiplied by ohms reduces to the units joules/second)

3) A power supply is used to pass a current of 1 A at 6 V through a mass of copper of 255 grams for 3 minutes. During this time the mass of copper is observed to rise by 10° C. (co-0.093 cal/g°C) (Lab 10, Joule Heat). a) calculate the electrical energy in J expended by the circuit b) calculate the heat energy delivered to the Cu in calories c) calculate the ratio of answer a) to that of b) d) calc. the percentage difference in c). Use a theoretical value of 4,18 J/cal. %3D

1. Including uncertainty, calculate the expected resistance of an orange-green-red-gold resistor. 2. A student wires a circuit. When the power supply is switched on, the ammeter reads I = 60 mA and the voltmeter reads V = 4.5 V.a) Use Ohm’s law to calculate the resistance of the resistor being measured.b) What should the student set the voltage to so the current in the resistor is 0.05 A? c) Assuming the resistor has a 10% tolerance, what the color code?

6) In recent class lectures, we discussed the temperature dependence of the electrical resistivity, p(T) for the three main classes of materials that conduct an electrical current; conductors, semiconductors, and superconductors. In the graph below, draw in by hand examples of the temperature dependence of the electrical resistivity, pT), for each material type. Give at least one example of each material type. plT) + +>T(K) 100 200 300