P2 REVISION – CHAPTER 2 – Electricity Answers Cables & Plugs Electric Circuits Electric symbols   Cell Open switch Bulb Diode Light emitting diode ammeter resistor Variable resistor fuse thermistor voltmeter What are the colours and names of the three wires inside a plug? Yellow and green – Earth Brown – Live Blue - neutral I is the current in amperes, A Q is the charge in coulombs, C t is the time in seconds, s. Every component has an agreed circuit symbol. Make sure you can recognise and draw them! Resistance Current is measured with an ammeter. Where are ammeters placed in relation to the component? In series What is the unit of current? Ampere The potential difference(pd) across a component is measured with a voltmeter. These are always placed in parallel with the component. What is the unit of potential difference? Volt What does each of the letters in the equation stand for? R is Resistance (Ω) V is voltage (V) I is current (A) Don’t forget units! KEY WORDS: Resistance Series Current Voltage Ampere Thermistor ASSESSMENT:   Ohm’s law: states that the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor. 1

P2 REVISION – CHAPTER 2 – Electricity Cont. Answers Current-Potential Difference Graphs Series Circuits A current-potential difference graph for a resistor. How are the components connected in a series circuit? In one loop one next to the other. What happens if there is a break in the circuit? Nothing in the circuit will work Is the current the same or different through each component? The same If you add together the potential difference what does it give you? The same as the p.d. over the battery. A current-potential difference graph for a filament bulb, line is a curve so the current is not directly proportional to the potential difference. Parallel Circuits The current in a diode flows in one direction only, in the reverse direction the diode has a very high resistance so the current will be what? 0 A How are the components connected in a parallel circuit? The components stack on top of eah other giving the current more tan one path to follow. What happens if there is a break in the circuit? Only the components on the same path will be affected. Is the pd across each component the same or different? The same The bigger the resistance of a component, the less the current through it. Thermistor: Resistance decreases if its temperature increases. LDR: resistance decreases if the light intensity on it increases. KEY WORDS: Diode Filament bulb Resistor Thermistor ASSESSMENT: 2

P2 REVISION – CHAPTER 2 – Electricity Cables & Plugs Electric Circuits Electric symbols   What are the colours and names of the three wires inside a plug? ___________________________________________________________________________ I is the current in amperes, A Q is the charge in coulombs, C t is the time in seconds, s. Every component has an agreed circuit symbol. Make sure you can recognise and draw them! Resistance Current is measured with an ammeter. Where are ammeters placed in relation to the component? _______________________________________________________ What is the unit of current?__________________ The potential difference(pd) across a component is measured with a voltmeter. These are always placed in parallel with the component. What is the unit of potential difference? ______________________ What does each of the letters in the equation stand for? R is __________________________________ V is __________________________________ I is __________________________________ Don’t forget units! KEY WORDS: Resistance Series Current Voltage Ampere Thermistor ASSESSMENT:   Ohm’s law: states that the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor. 3

P2 REVISION – CHAPTER 2 – Electricity Cont. Current-Potential Difference Graphs Series Circuits A current-potential difference graph for a resistor. How are the components connected in a series circuit? _______________________________________________________________ What happens if there is a break in the circuit? _______________________________________________________________ Is the current the same or different through each component? _______________________________________________________________ If you add together the potential difference what does it give you? _______________________________________________________________ A current-potential difference graph for a filament bulb, line is a curve so the current is not directly proportional to the __________________ ___________________. Parallel Circuits The current in a diode flows in one direction only, in the reverse direction the diode has a very high resistance so the current will be what? How are the components connected in a parallel circuit? ______________________________________________________________________ What happens if there is a break in the circuit? ______________________________________________________________________ Is the pd across each component the same or different? ________________________ The bigger the resistance of a component, the ______________ the current through it. Thermistor: Resistance _______________ if its temperature increases. LDR: resistance decreases if the light intensity on it ___________. KEY WORDS: Diode Filament bulb Resistor Thermistor ASSESSMENT: 4