Question

The first circuit we' investigate contains an inductor and a resistor hooked up in series with a constant votage source Set up a circuit battery a resistor a swhch, and an inductor, as shown in the figure and with the values indicated 20.00 Volts 0.00 Ohms When the switch is closed, what happens to the current in the circuit? (The intrinsic resistance of the indluctor is zero.) The current instantaneously becomes 1 A The curent gradually increases from zero to 2 A and then remains constant The current gradually increases from zero to 1 A and then remains conslant The current instantaneously becomes 2A Correct As described by Faraday's law of induction, the emf produced by the inductor (commonly reterred to as a back emt) is proportional to the rate of change of the current (since the magnetic fux is proportional to the current) The current cannot instantaneously increase from zero to 2 A since that would produce an ntnite back em once he current reaches a steady value there s no back em n te nductor, so the creuit tsidentcal to one with ist ฮ battery and ฮ resistor the resistance o the wire the Inductor 15 assumed to be essentil zero Part B For the circuit in the previous part, what happens if the inductance of the inductor is increased? O The amount of time for the curment to reach its maximum value decreases The macimum current (long ater the switch is closed) decreases The amount of tme for the current to reach its maximum value increases The maximum current (long aRer the switch is closed) increases.

Answer 1

For RL or LR circuit the value of current in the circuit at time t is given by I (t) = V/R (1 - e^-RT/L) where we define L/R = tau which is known as time constant time constant is defined as the required times for the current to reach its maximum value. therefore tau alpha L as L increase our tau also uparrow ses i.e. the time for the current to reach its maximum values increases So option (C) is correct