Electricity

• What is electric current? Electric current is the flow of electrical charge
• What is current measured in? Amps
• What is electric charge measured in? Coulombs
• How can you calculate charge flow? Charge flow = Current * Time Q=It
• What is the resistance of a component? The measure of how it resists the flow of charge
• What happens to the charge and current, if the resistance is high? [2] - The more difficult it is for charge to flow - The lower the current
• What is resistance measured in? Ohms
• What does potential difference (voltage) tell us? Difference in electrical potential from one point to another.
• What happens when the potential difference across a component is large? [2] - The greater the flow of charge through it's component - The bigger the current
• What is potential difference measured in? Volts using a voltmeter
• What is the equation for Ohms law? Potential Difference = Current * Resistance V=IR
• What are V-I graphs used to show? The relationship between the potential difference and current for any component.
• What does a straight line through the origin indicate? That the voltage and current are directly proportional
• What does a steep gradient indicate? A steep gradient indicates low resistance
• What does a shallow gradient indicate? A shallow gradient indicates a high resistance
• What is an ohmic conductor and what does it show? A resistor in which the current is directly proportional to the potential difference at a constant temperature. This means that the resistance remains constant as the current changes.
• What happens to the temperature as the current flows through a filament lamp increases? Increases.
• What happens to the current in a diode? [2] - Current in a diode will only flow in one direction. - The diode has a very high resistance in the reverse direction.
• What happens to the resistance in a Thermistor? The resistance of a thermistor decreases as the temperature increases.
• What happens to the resistance of an LDR? The resistance of an LDR decreases as light intensity increases.
• Electrical components can be connected in a ______ or ________ 1. Series 2. Parallel
• What is the current like through each component in a series circuit? It's the same through each component.
• What happens to the total potential difference supply in a series circuit? It is shared between the components
• Why is the total resistance of two components the sum of the resistance of each component? Current has to travel through each component in turn.
• What happens when you add resistors in a series circuit? Adding resistors increases the total resistance in ohms. Rtotal = R1 + R2
• What is the potential difference like in Parallel circuits? The potential difference across each component is the same.
• What is the total current the sum of in a parallel circuit? Sum of the currents flowing through the separate components.
• What is the total resistance of two resistors like in a parallel circuit? The total resistance of two resistors is less than the resistance of the smallest individual resistor.
• What happens when you add resistors to a parallel circuit? Adding resistors in parallel reduces the total resistance.
• What does the power of a device depend on? [2] - Potential difference across it - Current flowing through it
• Will a device with a higher potential difference or current use more energy per second than one with a lower potential difference or current? Yes.
• What is the equation for (current)2? Power = (current)2 * resistance P = I2 R
• What is a direct current supply? It is the type of current that is supplied by cells and batteries.
• What is an alternating current supply? It is the type of current used in mains electricty.
• What is the mains electricity in the UK? 230 volts
• What is the frequency in the UK? 50 Hertz
• How many cables does the main supply use? Three
• What is the colour and electrical potential of the live wire? [2] - Brown - 230V Potential
• What is the colour and electrical potential of the neutral wire? [2] - Blue - At o close to the 0V earth potential
• What is the colour and electrical potential of the earth wire? [2] - Green and yellow stripes - 0V Potential