Practice Test 4 Physics 112-1 F12 Page 1 of 5

Practice Test 4 Physics 112-1 F12 Page 1 of 5

Practice Test 4: Electric Current and Electric Circuits

Name ______

A fully charged car battery is to be connected by jumper cables to a discharged car battery in order to charge it. (Note: Batteries do not actually store charge. A ‘fully charged’ battery is one that contains the maximum amount of stored chemical energy.) To which terminal of the discharged battery should the positive terminal of the charged battery to be connected? Assume the charged battery has an emf of Ɛ1 = 12.0V, the discharged battery has an Emf of Ɛ1 = 11.0V, the internal resistances of the batteries are r1 = r2 = 0.020Ω, (assume you can approximate a car battery was an Emf and a resister in series) and the resistance of the jumper cables is R = 0.010Ω. What will be the charging current? What will be the current if the batteries are connected incorrectly?

Find the equivalent resistance in the circuit below. If the 4 resistors in the circuit have a power output of P1 = 500W, P2 = 600W, P3 =50W and P4 = 1500W, will the circuit be overloaded if the circuit draws 120V and 20A? In other words, will the circuit breaker – if there was one – pop?

Applying Kirchhoff’s Loop Laws, find the unknown Emf in the following circuit:

For the following circuit, find the current and potential through each resistor. Do we have the direction of the Emf correct in the circuit?

I hereby certify that all the work done on this exam is fully my own work, done without assistance and using only the calculator and equation sheet provided.

Signature ______Date ______

Extra Credit: (2points) A heater consists of a variable resistor (a resistor whose resistance can be varied) connected across an ideal voltage supply. (An ideal voltage supply is one that has a constant Emf and a negative internal resistance.) To increase the heat output, should you decrease the resistance or increase the resistance? Explain your answer.