Physics 111: Elementary Physics Pre-Lab Exercise Electric Current, Potential and
ID: 2144084 • Letter: P
Question
Physics 111: Elementary Physics
Pre-Lab Exercise
Electric Current, Potential and Power
Name: ____________________________ Section: ___________
Some typical data from this type of experiment are given below. Note that 1mA = 10-3 A.
V = 10.0 V Ra = 500 ? Rb = 1000 ?
Rc = 750 ? ia =10.7 mA ib = 4.6 mA ic =6.1 mA
Va = 5.4 V Vb = 4.6 V Vc = 4.6 V
1. Conservation of charge implies that at each branching point, or node, the current in should have the same value as the current out. Use the data to test the statement.
ia = ib + ic .
2. Conservation of energy tells us that the total energy provided to the circuit should balance the Joule heat losses in circuit. The rate at which the energy is provided, the input power, must therefore balance the rate at which the energy is converted to heat. Use the data to test the following relationship equating the power in to the power out. [Since the values of voltage and current above have been rounded to one decimal place your test of the equality below will not be exact]
iaV = ia2 Ra + ib2 Rb + ic2 Rc .
3. Conservation of energy also tells us that the voltage rises around any given loop should equal the voltage drops in the same loop. Use the data to test the following statements.
V = Va + Vb = Va + Vc .
4. State briefly (100 words or less) the objectives of this experiment and the principles which are to be tested.
Some typical data from this type of experiment are given below. Note that 1mA = 10-3 A. Conservation of charge implies that at each branching point, or node, the current in should have the same value as the current out. Use the data to test the statement. Conservation of energy tells us that the total energy provided to the circuit should balance the Joule heat losses in circuit. The rate at which the energy is provided, the input power, must therefore balance the rate at which the energy is converted to heat. Use the data to test the following relationship equating the power in to the power out. [Since the values of voltage and current above have been rounded to one decimal place your test of the equality below will not be exact] Conservation of energy also tells us that the voltage rises around any given loop should equal the voltage drops in the same loop. Use the data to test the following statements. State briefly (100 words or less) the objectives of this experiment and the principles which are to be tested.Explanation / Answer
1) ib + i = 4.6 + 6.1 = 10.7 so good
2)
ia V = 10.7E=3*10 = 10.7E-2
ia^2 Ra + ib^2 + rb + ic^2 Rc = 10.7E-3^2*500 + 4.6E-3^2*1000+ 6.1E-3^2*750=10.6E-2
so within rounding pretty good
3)
Va + Vb = 5.4 + 4.6 = 10
Va + Vc = 10
so good
4) Here we tested conservation of charge that is charge that flows in flows (part 1).
conservation of energy was tested in two ways. First that energy supplied is the same as energy
used in the resistors.(part 2) Secondly, that potential energy did not depend on path. (part 3)