Electricity
- 2. Atoms… Have neutrons , protons , and electrons . Protons are positively charged Electrons are negatively charged
- 3. Electrons… Are located on the outer edges of atoms…they can be moved . A concentration of electrons in an atom creates a net negative charge. If electrons are stripped away, the atom becomes positively charged.
- 4. The world is filled with electrical charges : + - + + + + + + + + + - - - - - - - - -
- 5. What is this electrical potential called? Static Electricity - - - - - - - + + + + +
- 6. Static Electricity The build up of an electric charge on the surface of an object. The charge builds up but does not flow. Static electricity is potential energy . It does not move. It is stored .
- 7. Static Discharge… Occurs when there is a loss of static electricity due to three possible things: Friction - rubbing Conduction – direct contact Induction – through an electrical field (not direct contact)
- 8. Electricity that moves … Current : The flow of electrons from one place to another. Measured in amperes (amps) Kinetic energy
- 9. How can we control currents? With circuits . Circuit : is a path for the flow of electrons. We use wires .
- 10. There are 2 types of currents: Direct Current (DC) – Where electrons flow in the same direction in a wire.
- 11. There are 2 types of currents: Alternating Current (AC) – electrons flow in different directions in a wire
- 12. simple circuits Here is 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
- 13. simple circuits When the 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.
- 14. circuit diagram battery switch lamp wires Scientists usually draw electric circuits using symbols;
- 15. circuit diagrams In circuit diagrams components are represented by the following symbols; battery switch motor ammeter voltmeter resistor
- 16. types of circuit There are two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS
- 17. The components are connected 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.
- 18. PARALLEL CIRCUITS The current 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.
- 19. measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A
- 20. measuring current This is how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT A A
- 21. measuring current SERIES CIRCUIT 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
- 22. Conductors vs. Insulators Conductors – material through which electric current flows easily . Insulators – materials through which electric current cannot move .
- 23. Examples Conductors : Metal Water Insulators : Styrofoam Rubber Plastic Paper
- 24. What is Resistance? The opposition to the flow of an electric current, producing heat . The greater the resistance, the less current gets through. Good conductors have low resistance. Measured in ohms.
- 25. What Influences Resistance? Material of wire – aluminum and copper have low resistance Thickness – the thicker the wire the lower the resistance Length – shorter wire has lower resistance Temperature – lower temperature has lower resistance
- 26. What is Voltage? The measure of energy given to the charge flowing in a circuit. The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit.
- 27. Difference between Volts and Amps Example – you could say that… Amps measure how much water comes out of a hose. Volts measure how hard the water comes out of a hose.
- 28. Ohm’s Law Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. Resistance = Voltage / Current Ohms = Volts / Amps
- 29. Practice with Ohm’s Law 8 48 6 5 45 9 15 30 2 10 150 15 25 100 4 Amps Volts Ohms