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Electric circuits
The document discusses electrical circuits and Ohm's Law. It defines key concepts like voltage, current, resistance and their relationships. Voltage is measured in volts and is the "push" that drives current through a circuit. Current is measured in amps and is the flow of electrons. Resistance opposes the flow of current. Ohm's Law states that current is directly proportional to voltage and inversely proportional to resistance. Circuits can be connected in series or parallel, affecting how current and voltage are distributed.
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Electric circuits
- 1.
- 2. OBJECTIVES 1) Statethe relationship between voltage, current and resistance; 2) Apply ohm’s law in solving problems
- 3. Electric Current Currentis the rate of flow of electrons/charge - It is abbreviated as I - It is measured in amperes - One ampere is defined as one coulomb of electrons flowing past a point each second (Q/s)
- 4. VOLTAGE - Voltageis a force that pushes/drives the electrons/charge - It is also referred to as electromotive force or difference in potential. - It is abbreviated as E or EMF - Voltage is measured in volts (v) Voltage source will have a polarity (negative and positive side) Current flows from negative to positive (changing conventions) AC/DC: Alternating current (polarity of source reverses) or Direct current (polarity is constant)
- 5. RESISTANCE Resistances arethe barriers to the flow of charge It is abbreviated as R It is measured in ohms
- 6. S.MORRIS 2006 ELECTRICALCIRCUITS More free powerpoints at www.worldofteaching.com
- 7. The CELL Thecell stores chemical energy and transfers it to electrical energy when a circuit is connected. When two or more cells are connected together we call this a Battery . The cells chemical energy is used up pushing a current round a circuit.
- 8. What is anelectric current? An electric current is a flow of microscopic particles called electrons flowing through wires and components. + - In which direction does the current flow? from the Negative terminal to the Positive terminal of a cell.
- 9. simple circuits Hereis a simple electric circuit. It has a cell, a lamp and a switch. To make the circuit, these components are connected together with metal connecting wires. cell lamp switch wires
- 10. simple circuits Whenthe switch is closed, the lamp lights up. This is because there is a continuous path of metal for the electric current to flow around. If there were any breaks in the circuit, the current could not flow.
- 11. circuit diagram cellswitch lamp wires Scientists usually draw electric circuits using symbols;
- 12. circuit diagrams Incircuit diagrams components are represented by the following symbols; cell battery switch lamp motor ammeter voltmeter buzzer resistor variable resistor
- 13. types of circuitThere are two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS
- 14. The components areconnected end-to-end, one after the other. They make a simple loop for the current to flow round. SERIES CIRCUITS If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.
- 15. PARALLEL CIRCUITS Thecurrent has a choice of routes. The components are connected side by side. If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.
- 16. measuring current Electriccurrent is measured in amps (A) using an ammeter connected in series in the circuit. A
- 17. measuring current AA This is how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT
- 18. measuring current SERIESCIRCUIT PARALLEL CIRCUIT current is the same at all points in the circuit. 2A 2A 2A current is shared between the components 2A 2A 1A 1A
- 19. copy the followingcircuits and fill in the missing ammeter readings. ? ? 4A 4A 4A 3A ? ? 1A ? 3A 1A 1A
- 20. measuring voltage The‘electrical push’ which the cell gives to the current is called the voltage . It is measured in volts (V) on a voltmeter V
- 21. Different cells producedifferent voltages. The bigger the voltage supplied by the cell, the bigger the current. measuring voltage Unlike an ammeter a voltmeter is connected across the components Scientist usually use the term Potential Difference (pd) when they talk about voltage.
- 22. measuring voltage VThis is how we draw a voltmeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT V
- 23. V measuring voltageV V V
- 24. series circuit 1.5Vvoltage is shared between the components 1.5V 3V
- 25. voltage is the same in all parts of the circuit. 3V parallel circuit 3V 3V
- 26. measuring current &voltage copy the following circuits on the next two slides. complete the missing current and voltage readings. remember the rules for current and voltage in series and parallel circuits.
- 27. measuring current &voltage V V 6V 4A A A a)
- 28. measuring current &voltage V V 6V 4A A A A b)
- 29. answers 3V 3V6V 4A 4A 6V 6V 6V 4A 4A 2A 2A 4A a) b)