1. Electrical circuits

2. Intensity (I): Number of charges that flow past a given point every second. Measured in Amperes (A). Wires that carry the electrical charges. Potential difference (V): The amount of energy transferred between two charges. Measured in volts (V). Power supply Resistance: a force that hinders the flow of the current. This is measured in ohms (Ω). Element that uses electrical energy. Characteristics of current in a circuit

3. Types of circuits Series circuits No alternate routes for the charge. If one element is defective the charge cannot travel. Zigzag represents an appliance, something that uses up electricity (light bulb, etc.)

4. Types of circuits Parallel circuit When a circuit branches out at least once. If one element is defective, the charge continue to flow.

5. Symbols in a circuit diagram The symbol for an ammeter is And for a voltmeter it’s Both are resistive circuit elements. Ammeters must be wired directly into the circuit - in series with the resistors like this A voltmeter must be put in parallel with the resistor to measure the voltage drop across it:

6. Important Information

7. Problems R = 20 Ω I = ?A R = 30 Ω R = 10 Ω V = 9 V I = 0.13 A What’s the equivalence resistance? And what’s the unknown intensity?

8. Problems R = 10 Ω V = ? V R = 10 Ω VT = 2 V IT = 20 A What’s the equivalence resistance? What’s the unknown potential difference?

9. Ohm’s Law

10. I V R

11. Exam Problems Calculate the total current flowing in the circuit: and the voltage drop in each resistor.

12. Problems Calculate the current in each branch of this circuit:

13. 1. Three 20-ohm resistors are connected in series across a 120-volt generator. a) What is the total resistance of the circuit? b) What current flows in the circuit?

14. 2. A 10-ohm resistor, a 15-ohm resistor, and a 5-ohm resistor are connected in series across a 90-volt battery. a) What is the total resistance of the circuit? b) What current flows through the circuit?

15. 3. Ten Christmas tree bulbs are of equal resistance. When connected to a 120-volt outlet, a current of 0.5 amp flows through the bulbs. a) What is the total resistance of the circuit? b) What is the resistance of each bulb?

16. 4. Three 15-ohm resistors are connected in parallel and placed across a difference in potential of 30 volts. a) What is the total resistance of the parallel circuit? b) What current flows through the entire circuit? c) What current flows through each branch of the circuit?

17. 5. Two 10-ohm resistors are connected in parallel and placed across the terminals of a 15-volt battery. a). What is the total resistance of the parallel circuit? b) What current flows in the circuit? c) What current flows through each branch of the circuit?

18. Parallel-series circuits

19. Note It’s important to realize that resistors in parallel act as one. Each of these can be regarded to one resistor What’s the equivalent resistance?

20. Problems Find the readings on the meters in the circuit: