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Minute Paper (2/16/04) Open circuit vs. short circuit Current direction: high voltage to low voltage, except inside the source.  Where do KVL & KCL.

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Presentation on theme: "Minute Paper (2/16/04) Open circuit vs. short circuit Current direction: high voltage to low voltage, except inside the source.  Where do KVL & KCL."— Presentation transcript:

1 Minute Paper (2/16/04) Open circuit vs. short circuit Current direction: high voltage to low voltage, except inside the source.  Where do KVL & KCL come from? –Maxwell eqs. and charge conservation.

2 Good Lab. Practice Make circuits neat Check the circuit before turning on power, and turn power if you need change circuit elements. Do not touch the circuit with bare hand when power is on. Make sure the grounding is good When using meters, start with large range first Do not short voltage source or open current source.

3 Series Resistors and the Voltage Divider Rule Series Circuit: One branch  same current through each resistor. Voltage Divider:

4 Example: voltage divider If you want to use your car battery (12 V) to power your laptop computer which requires 3V power supplier, how would you do it.

5 Practical voltage sources Ideal voltage source: r s =0 The output voltage is now depend on the R L Make r s << R L, so v L  v S, independent on R L

6 Parallel Resistors and the Current Divider Rule Current Divider: Parallel Circuit: resistors share the same terminal  same voltage on each resistor. Large current though smaller R Advantage of parallel circuit: a broken branch will not affect other branches

7 Practical current sources Ideal current source: r s =∞ The output current is now depend on the R L Make r s >> R L, so i L  i S, independent on R L

8 Ammeter Ammeter: –measure current, –put in series, –The lower the internal resistance is, the better the meter is

9 Voltmeter Voltmeter: –measure voltage, –put in parallel, –the higher the internal resistance is, the better the meter is.

10 An example: parallel circuit There is a circuit break in circuit that supplies power to your kitchen. The circuit break will be triggered if the total current exceeds 25 A. Can you turn on a 1500W toaster, a 1000W dishwasher, a 1000 W microwave oven, and 1000W refrigerator simultaneously?

11 Concept Check There are three identical batteries rated 1.5V and max. output current is 200 mA. If they are connected in series, –what is total output voltage? –What is max. output current? If they are connected in parallel, –what is total output voltage? –What is max. output current?

12 Simple circuit analysis: Apply element combination rules

13 Example


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