Gr.12 Ohm_s Law in AC Lesson3 Physics.pptx

Physics 12 grade Ohm's Law in AC

1. Today’s Objectives Represent a sinusoidally alternating current or voltage by an equation of the form x = x max sin ωt Theme: Sinusoidal Representation of AC Current and AC Voltage

2. What other graph has the same shape as this graph? How can we graphically represent an alternating current? A graph to represent a sinusoidal Alternating Current

3. the current varies cyclically Current is positive during half of the cycle and negative in the other half When mains appliance is used, current flows backwards and forwards in wires between you and the power station where I t is being generated Characteristics of Alternating Current A graph to represent a sinusoidal Alternating Current Recall

4. For the value of current at any time Equation for a.c.       And the frequency and period are related by:   I is the peak value of the a.c. found on the highest point on the graph.

5. Sample Problem 1 :

6. Answers

7. Image of generators Alternating Voltages Recall: An e.m.f. V varies sinusoidally and it takes the same form as the the equation for a.c.    

8. Sample Problem 2 :

9. Answer

10. ‹#› To sum up, in RLC series circuit: The instantaneous voltage would be given by V = V o sin ωt The instantaneous current would be given by I = I o sin ( ωt - φ ) ι = I max sin ( ωt - φ ) φ is the phase angle between the current and the applied voltage Since the elements are in series, the current at all points in the circuit has the same amplitude and phase

11. For Resistor in AC circuit The current is in phase with the voltage Recall:

12. Resistor in AC circuit

13. Capacitor in AC circuit   Recall:

14. Capacitor in AC circuit

15. Inductor in AC circuit   Recall:

16. Inductor in AC circuit

17. Sample Problem 3 : A sinusoidal, 60.0-Hz, ac voltage is read to be 120 V by an ordinary voltmeter. What is the maximum value the voltage takes on during a cycle? What is equation for the voltage?

18. Answer

19. A voltage v = (60.0 V) sin 120 𝞹 t is applied across a 20.0-𝞨 resistor. What will an ac ammeter in series with the resistor read? Sample Problem 4:

20. Answer

21. It’s your turn! Students’ Work