Flashcards in Deck 3 = Physics Summer Term Deck (46):
Electrical current is...
-The movement or flow of charge.
What is charge shown as and measured as equations?
-(Q) measured in coulombs (C).
What is current shown as and measured in, in equation?
-(I) and measured in amps, (A).
Current in a series circuit?
-Current is equal all round circuit.
Which way do electrons flow?
-Electrons repelled by the negative terminal on the battery.
If you open switch on a series circuit what happens to the current?
-The current drops to 0.
What is conventional current?
-Conventional current is the direction from positive to negative around the circuit. Electrons actually flow the other way being, negatively charged. They repelled by the negative charge of the battery.
What is the equation for charge?
-The equation for charge is. Charge = current x time. (Q=IT)
If a current of 2 amps flows for three seconds the charge delivered 6 C...
Current in parallel circuits?
-The current in the branches of the parallel circuits adds up to the current in the battery. (Pg 1 book 2).
Equations of charge?
What is current measured in?
-Current is measured in amps (A)
What is charging measured in?
-Charge is measured in coulombs (C)
What is Time measured in?
-Time is measured in seconds (s)
One amp is the same as...
-1 Coulomb every second.
What is voltage?
-Voltage is the energy transferred per unit charge... between two points in the circuit.
Equation for energy transfer?
-E=QV energy transferred = charge x voltage.
What is voltage Measured in?
-Voltage is measured in volts V.
What is charge Measured in?
-Charge is measured in coulombs C.
What is energy transfer measured in?
-Energy transfer is measured in watts W.
Voltage in a series circuit?
-Voltage across the components is equal to the voltage across the battery.
Voltage is also known as...
In the circuit as the electrons flow through the bulbs...
-They lose some of their potential energy.
In total, all the energy supplied by the battery?
-Is radiated by the bulbs, almost none is spent in the connecting wires.
What is electrical resistance?
-Resistance is measured in ohms. It tells us how much a component resist the flow of current.
What is the equation to calculate resistance?
-Resistance = voltage / current. (R = V/I).
How does the resistance of a filament bulb change with voltage?
-The resistance of the bulb increases as the voltage increases.
What is a thermistor?
-Its resistance decreases as the temperature increases. the opposite of a filament.
What is ohms law?
-Ohm's law states that the resistance is constant at constant temperature. An I-V graph that is a straight line through the origin shows that a component obeys Ohm's law. Wires and resistors obey ohms law this is why they are called 'Ohmic components'.
What components do not obey Ohm's law?
-Filament bulbs ,diodes and thermistors do not obey ohm's law therefore they are called 'non-ohmic components.'
What is a diode?
-Diodes have a high resistance for current flowing in one direction and a low resistance to current flowing in the other direction. Therefore they are used to convert alternating-current to direct current.
In a plug what colour is the neutral wire?
-The neutral wire has blue insulation.
In the plug what colour is it earth wire?
-The earth wire is green and yellow.
In a plug what colour is the live wire?
-The live wire has brown insulation.
What is the mains supply voltage in the United Kingdom?
What type of current is the mains electricity in United Kingdom?
-Mains current in United Kingdom is alternating-current this means that it flows from positive to negative.
Equation for power?
-Power = voltage x current W = V x A
What fuse must be used in a plug?
-The fuse must be greater than the normal current through the appliance, this is close to it as possible so that the fuse will blow as soon as the current gets too high.
What is a fuse?
-Fuse is a thin piece of wire in a glass bulb in series with the live wire. As soon as the current gets too high the fuse will melt breaking the circuit.
What is double insulation?
-Occasionally installation may become worn in a wire or may melt. If the device has a metal casing it must have a second layer of insulation beneath the casing in case the wire insulation fails. This is double insulation.
How can the live wire be used for safety?
-The earth wire is attached to the metal casing. Is the casing becomes live the Earth wire will complete the circuit. A large current will flow through melting the fuse making the device safe.
What is the frequency of alternating-current in the mains on the United Kingdom?
Like charges repel...
-Unlike charges attract.
What is a insulator?
-This is a material that electrons can not flow through due to high resistance.
What is a conductor?
-This is a material that has a sea on localized electrons there for electrons can more freely.