Presentation is loading. Please wait.

Presentation is loading. Please wait.

Today5/7  Questions?  Circuits and Capacitors  Course Evaluations.

Similar presentations


Presentation on theme: "Today5/7  Questions?  Circuits and Capacitors  Course Evaluations."— Presentation transcript:

1 Today5/7  Questions?  Circuits and Capacitors  Course Evaluations

2 Capacitors Capacitance tells me how many coulombs of charge are stored in a capacitor when it has 1 Volt across it. A 25  F capacitor will have 25  C of charge on it when it has 1 volt across it. Think of capacitance as “coulombs per volt”. Units:coulombs per volt or “Farads” Equation: C = q/V

3 Capacitors and Energy How many Joules of energy are stored in the capacitor? 12 V 6F6F As the battery moves charge from one plate to another, the potential difference increases from zero to 12 V. The average is 6 V and the energy stored is q times 6 V (q  V ave ). Energy = q  V ave = 1 / 2 q  V = 1 / 2 C  V 2 C = q/  V

4 Kirchhoff’s Rules, Loop  The sum of all voltages around any closed loop is zero. (what goes up must come down)  or  V A,A = 0  !!must keep track of ups and downs!! (+/-)

5 Kirchhoff’s Rules, Junction  The sum of all currents at any junction is zero. (what goes in must come out)  !!must keep track of ins and outs!! (+/-)

6 Capacitors with Resistors Will current flow when the switch is closed? 12 V 6F6F 66 6F6F Yes, but only for an instant until the capacitor is charged. Yes, but it will take longer to charge the capacitor.

7 Capacitors with Resistors Describe current and voltage long after the switch has been closed. 12 V 6F6F 66 6F6F No current, 12 V across the capacitor. No current, 12 V across the capacitor, zero V across the resistor. Loop rule still applies! V = IR for resistors still applies!

8 Capacitors with Resistors Describe current and voltage long after the switch has been closed. 12 V 6F6F 22 2 Amps through the battery and both resistors. 4 V across 2  and 8 V across the capacitor and 4  Loop rule still applies! V = IR for resistors still applies! 44


Download ppt "Today5/7  Questions?  Circuits and Capacitors  Course Evaluations."

Similar presentations


Ads by Google