2.
Atoms… <ul><li>Have neutrons , protons , and electrons . </li></ul><ul><li>Protons are positively charged </li></ul><ul><li>Electrons are negatively charged </li></ul>
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Electrons… <ul><li>Are located on the outer edges of atoms…they can be moved . </li></ul><ul><li>A concentration of electrons in an atom creates a net negative charge. </li></ul><ul><li>If electrons are stripped away, the atom becomes positively charged. </li></ul>
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The world is filled with electrical charges : + - + + + + + + + + + - - - - - - - - -
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What is this electrical potential called? <ul><li>Static Electricity </li></ul>- - - - - - - + + + + +
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Static Electricity <ul><li>The build up of an electric charge on the surface of an object. </li></ul><ul><li>The charge builds up but does not flow. </li></ul><ul><li>Static electricity is potential energy . It does not move. It is stored . </li></ul>
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Static Discharge… <ul><li>Occurs when there is a loss of static electricity due to three possible things: </li></ul><ul><ul><ul><li>Friction - rubbing </li></ul></ul></ul><ul><ul><ul><li>Conduction – direct contact </li></ul></ul></ul><ul><ul><ul><li>Induction – through an electrical field (not direct contact) </li></ul></ul></ul>
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Electricity that moves … <ul><li>Current : The flow of electrons from one place to another. </li></ul><ul><li>Measured in amperes (amps) </li></ul><ul><li>Kinetic energy </li></ul>
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How can we control currents? <ul><li>With circuits . </li></ul><ul><li>Circuit : is a path for the flow of electrons. We use wires . </li></ul>
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There are 2 types of currents: <ul><li>Direct Current (DC) – Where electrons flow in the same direction in a wire. </li></ul>
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There are 2 types of currents: <ul><li>Alternating Current (AC) – electrons flow in different directions in a wire </li></ul>
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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
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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.
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circuit diagram battery switch lamp wires Scientists usually draw electric circuits using symbols;
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circuit diagrams In circuit diagrams components are represented by the following symbols; battery switch motor ammeter voltmeter resistor
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types of circuit There are two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS
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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.
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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.
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measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A
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measuring current This is how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT A A
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measuring current SERIES CIRCUIT PARALLEL CIRCUIT <ul><li>current is the same </li></ul><ul><li>at all points in the </li></ul><ul><li>circuit. </li></ul>2A 2A 2A <ul><li>current is shared </li></ul><ul><li>between the </li></ul><ul><li>components </li></ul>2A 2A 1A 1A
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Conductors vs. Insulators <ul><li>Conductors – material through which electric current flows easily . </li></ul><ul><li>Insulators – materials through which electric current cannot move . </li></ul>
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What is Resistance? <ul><li>The opposition to the flow of an electric current, producing heat . </li></ul><ul><li>The greater the resistance, the less current gets through. </li></ul><ul><li>Good conductors have low resistance. </li></ul><ul><li>Measured in ohms. </li></ul>
25.
What Influences Resistance? <ul><li>Material of wire – aluminum and copper have low resistance </li></ul><ul><li>Thickness – the thicker the wire the lower the resistance </li></ul><ul><li>Length – shorter wire has lower resistance </li></ul><ul><li>Temperature – lower temperature has lower resistance </li></ul>
26.
What is Voltage? <ul><li>The measure of energy given to the charge flowing in a circuit. </li></ul><ul><li>The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit. </li></ul>
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Difference between Volts and Amps <ul><li>Example – you could say that… </li></ul><ul><ul><li>Amps measure how much water comes out of a hose. </li></ul></ul><ul><ul><li>Volts measure how hard the water comes out of a hose. </li></ul></ul>
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Ohm’s Law Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. <ul><li>Resistance = Voltage / Current </li></ul><ul><li>Ohms = Volts / Amps </li></ul>
29.
Practice with Ohm’s Law 8 48 6 5 45 9 15 30 2 10 150 15 25 100 4 Amps Volts Ohms
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