R 20 The switch in the circuit is closed at t 0 V 10V L 10H L 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 di dt 1 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 2 Clicker Question The switch in the circuit below is closed at t 0 R 20 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 3 1 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 4 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 5 Clicker Question The switch in the circuit below is closed at t 0 V 10 V 10V V 10 R 20 V 0 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 R 20 At t 0 V 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 7 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 8 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 9 3 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 10 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 11 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 12 4 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 13 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 14 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 15 5 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 16 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 peak 2 1 1 P t i peak V peak 2 2 Pave irmsVrms Same form as before but now RMS values 17 CT 33 34 A light bulb is attached to a wall plug 120 VAC 60 Hz How many times a second is the instantaneous power output to the bulb equal to zero A Never there is always power B 30 times sec C 60 times sec D 120 times sec E Other 18 6 CT 33 35 A 100 W light bulb is attached to a wall plug 120 VAC 60 Hz What is the peak power output to the bulb A 100 W B Sqrt 2 100 W 141 W C 200 W D Other 19 CT 33 36 A 600 Watt hairdryer is attached to 120 VAC circuit What is the peak current through the hairdryer to within 5 A 0 A B 5 A E Other C 7 A D 10 A 20 CT 33 37 The instantaneous power consumed by my De luxe Toaster Oven looks like this as a function of time 21 7 CT 33 38 1200 W Which of the following is correct P ave V …
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