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Electrical circuits. Characteristics of current in a circuit. Intensity (I): Number of charges that flow past a given point every second. Measured in Amperes (A). Wires that carry the electrical charges.
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Characteristics of current in a circuit • 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.
Types of circuits Zigzag represents an appliance, something that uses up electricity (light bulb, etc.) • Series circuits • No alternate routes for the charge. If one element is defective the charge cannot travel.
Types of circuits • Parallel circuit • When a circuit branches out at least once. If one element is defective, the charge continue to flow.
Problems R = 20 Ω I = ?A R = 30 Ω V = 9 V I = 0.13 A R = 10 Ω R = 10 Ω What’s the equivalence resistance? And what’s the unknown intensity?
Problems R = 10 Ω R = 10 Ω R = 10 Ω R = 10 Ω V = ? V VT = 2 V IT = 20 A What’s the equivalence resistance? What’s the unknown potential difference?
Ohm’s Law V I R
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?
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?
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?
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?
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?
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?