R 20 V 10 V The switch in the circuit is closed at t 0 L 10 H L di dt What is the initial current in the inductor immediately after the switch is closed at t 0 A 0 A B 0 5 A C 1 0 A D 2 A E None of these 1 R 20 V 10 V The switch in the circuit is closed at t 0 L 10 H L di dt What is the initial current in the inductor immediately after the switch is closed at t 0 A 0 A B 0 5 A C 1 0 A D 2 A E None of these 2 CAPA 13 is due Friday New online participation survey is still up Reading 34 3 5 Last Inductors in circuits Today Inductors and AC circuits Next Maxwell s equations putting it all together 3 1 Clicker Question The switch in the circuit below is closed at t 0 What is the initial rate of change of current di dt in the inductor immediately after the switch is closed R 20 V 10 V L 10 H A 0 A s B 0 5A s C 1A s D 10A s E None of these Hints What is the initial current through the circuit Given that what is the initial voltage across the inductor 4 Clicker Question The switch in the circuit below is closed at t 0 V 10V Before t 0 V V R 20 L 10H What is the initial rate of change of current di dt in the inductor immediately after the switch is closed A 0 A s B 0 5A s C 1A s D 10A s E None of these Hints What is the initial current through the circuit Given that what is the initial voltage across the inductor V 0 L di dt 5 Clicker Question The switch in the circuit below is closed at t 0 R 20 Before t 0 V V 0 V 10V L 10H What is the initial rate of change of current di dt in the inductor immediately after the switch is closed A 0 A s B 0 5A s C 1A s D 10A s E None of these Hints What is the initial current through the circuit Given that what is the initial voltage across the inductor V 0 6 2 Clicker Question The switch in the circuit below is closed at t 0 V 10 V 10V V 10 V 0 R 20 L 10H What is the initial rate of change of current di dt in the inductor immediately after the switch is closed A 0 A s B 0 5A s C 1A s D 10A s E None of these Hints What is the initial current through the circuit Given that what is the initial voltage across the inductor V 0 7 Clicker Question The switch in the circuit below is closed at t 0 V 10 V 10V R 20 At t 0 V L 10 What is the initial rate of change of current di dt in the inductor immediately after the switch is closed A 0 A s B 0 5A s C 1A s D 10A s E None of these Hints What is the initial current through the circuit Given that what is the initial voltage across the inductor V 0 di L dt 8 Clicker Question The switch in the circuit below is closed at t 0 V 10 R 20 V 10V V 10 briefly L 10H What is the initial rate of change of current di dt in the inductor immediately after the switch is closed A 0 A s B 0 5A s C 1A s D 10A s E None of these Hints What is the initial current through the circuit Given that what is the initial voltage across the inductor V 0 9 3 Clicker Question The switch in the circuit below is closed at t 0 V 10 R 20 V 10V V 10 briefly L 10H What is the initial rate of change of current di dt in the inductor immediately after the switch is closed A 0 A s B 0 5A s C 1A s D 10A s E None of these Hints What is the initial current through the circuit Given that what is the initial voltage across the inductor V 0 L di dt Answer I initial 0 so it must still be 0 Thus V across R 0 V across inductor V batt but also V inductor L di dt So at t 0 di dt V batt L 10V 10H 1 A s 10 Clicker Question An LR circuit is shown below Initially the switch is open At time t 0 the switch is closed What is the current thru the inductor L immediately after the switch is closed time 0 R1 10 V 10V L 10H R2 10 A Zero B 1 A C 0 5A D None of these 11 Clicker Question An LR circuit is shown below Initially the switch is open At time t 0 the switch is closed R1 10 V 10V L 10H R2 10 After a long time what is the current from the battery A 0A B 0 5A C 1 0A D 2 0A E None of these 12 4 AC Circuits The Voltage in your wall sockets at home is AC AC stands for Alternating Current but would perhaps more appropriately be called Alternating Voltage Alternating Sinusoidal with time 13 V t V peak sin t 2 f 2 T is the radial frequency radians second f is the frequency in cycles second Hertz T is the period in seconds i e time for one cycle 14 In the United States of America f 60 cycles second or Hertz T 1 60 seconds Vpeak 170 Volts One might be interested in something like the average Voltage But the average V t 0 15 5 Vrms V root mean square V2 Time Average of Voltage squared Vrms V p sin 2 t V p 1 2 V p 2 Time Average of sin2 or cos2 over many cycles 1 2 Vrms 170V 2 120 Volts This is how we refer to the US Standard Voltage 16 The term AC Voltage or VAC means Vrms V peak 2 The term AC Current somewhat redundant means irms i peak 2 RMS values of AC Voltage and Current are always implied if not explicitly stated otherwise This is because the old DC formulas involving V i R P power all hold for AC circuits if we use the RMS values 17 Example AC Voltage across a resistor V t V p sin t VAC R i t V V p sin t i peak sin t R R P t iV i peakV p sin 2 t Instantaneous Power is oscillating from zero to maximum 18 6 We might be interested in the average over time power delivered to the resistor P t iV i peakV peak sin 2 t 1 P t i peakV peak sin 2 t i peakV …
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