Question

4. The following questions refer to the RC circuit shown below 7.5 Ω 15Ω 250 15 v (a) (10 points) What is the time constant for this circuit? (b) (6 points) What will be the current immedistely atar the switch is cloed 12. arent lin por Tkis s the iciprocal (c) (5 points) What will be the current in the circuit after 0.5 ms? e resolt resistance, do you expect the current to reach the value from part (c) faster or slower than before? Explain. (d) (8 points) If the 7.5Ω resistor were to be replaced by another one with a higher enersy

a) what is the time constant for this circuit?

b) what will be the current immediately after switch is closed

c) what will be the current in the circuit after 0.5 ms?

d) if the 7.5 ohm resistor were to be replaced by another one with a higher resistance, do you expect the current to reach the value from part (c) faster or slowet than before? explain.

Answer 1

Times constant (tau) = Req C = 11.84 times 65 times 10^-6 tau = 769.6 mu s current immediately after closing switch = 25/11.84 = 1.267 A Rightarrow i_0 = 1.267 A i = i_0 e^-t/RC Rightarrow i = 1.267 e^- 0.5 times 10^-3/769.6 times 10^-6 = 1.267 e^-0.6497 = 0.61163 A i = 0.61163 A If 7.5 Ohm is replaced with higher one then overall resistance will increase then time constant will also increase then it will reach slowly.