Electricity (pt.1)

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What is electric current?
Flow of electric charge (electrons).
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What is current measured in?
Amperes, A
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Current will only flow in a _______ circuit...
Closed
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...if there is _______.
Potential difference
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What is potential difference?
The driving force that pushes the charge around.
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What is potential difference measured in?
Volts, V
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What is resistance?
Anything in a circuit that slows the flow down.
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What is measured in Amperes, A?
Current
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What is measured in Volts, V?
Potential difference
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What is measured in Coulombs, Q?
Charge
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What is measured in Ohms, Ω ?
Resistance
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The greater the resistance flowing through a component, the ______ the current that flows through.
Smaller
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Total charge depends on ______ and ______.
Current and time
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What is the formula?
Q=It
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What does "Q" stand for in the formula?
Charge
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What does "I" stand for in the formula?
Current
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What does "t" stand for in the formula?
Time
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What is time measured in?
Seconds
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More charge flows what there is a ______.
Bigger current flow
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What is the formula that links potential difference and resistance?
V=IR
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what does the "V" stand for in the formula?
Potential difference
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what does the "I" stand for in the formula?
Current
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what does the "R" stand for in the formula?
Resistance
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What is the symbol for current?
I
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What is the symbol for resistance?
Ω
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What is the symbol for time?
t
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What is the symbol for charge?
Q
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What id the symbol for potential difference?
V
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What is an example of an ohmic conductor?
Wire, resistor.
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What does not change in ohmic conductors?
Resistance, R
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When does it not change?
When the temperature is constant.
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Why does it not change?
Because the current is directly proportionate to the potential difference across it.
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When is this not the case (components)?
Filament bulb, diode.
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Why does it change in the bulb?
Some of the energy from the electric charge is moved to the thermal energy store.
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The bulb heats up when it is turned on. What increases with the temperature?
Resistance
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As the ______ so does the resistance?
Current
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When does the resistance change in diodes?
When the direction of the current is reversed.
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Ohm's Law: Current between two points is directly proportional to the ______ across the points.
Voltage
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Current through a resistor is directly proportionate (at a constant temperature) to the ______.
Potential difference
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What does and I-V characteristic graph refer to?
How the current flowing through a component changes as the potential difference across it changes.
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What does the I-V characteristic graph look like for ohmic conductors?
A straight, diagonal line.
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What does the I-V characteristic graph look like for filament bulbs?
An "S" curve.
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What does the I-V characteristic graph look like for diodes?
A flat then rising line.
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I-V characteristic graphs for non ohmic resistors are ______.
Non linear
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I-V characteristic graphs for ohmic resistors are ______.
Linear
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What happens to cell potential difference in series circuits?
It adds up.
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What then happens to the total potential difference of the cells?
It is equally shared by all the components.
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Ammeters are always placed in ______.
Series
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Voltmeters are always placed in ______.
Parallel
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In series circuits the current ______.
Stays the same everywhere.
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What happens to the resistance in series circuits?
It adds up.
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The bigger a component's resistance, the bigger its share of ______.
Potential difference
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In parallel circuits each component is ______ connected to the power supply.
independently
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If you disconnect one component in a parallel circuit will the circuit be affected?
Hardly
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If you disconnect one component in a series circuit will the circuit be affected?
It will stop working completely
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What happens when you add resistors in a parallel circuit?
The total resistance decreases.
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Why does this happen? (1)
As you add another loop the current has more directions to flow in.
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Why does this happen? (2)
As the crrent flows in more directions, the total current is increased which also decreases the total resistance.
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What does a graph of resistance against the number of identical resistors look like in a parallel circuit?
As the number of resistors increase the, the resistance goes down. A decreasing curve.
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What does a graph of resistance against the number of identical resistors look like in a series circuit?
As the number of resistors increase the, the resistance goes up. A diagonal line.
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What is the build up of static electricity caused by?
Friction
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What would happen if two insulating materials are rubbed together?
Some of the electrons will be scraped off onto the other.
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What will this cause?
One material will be positively charged and the other one would be negatively charged.
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Polythene ______ and acetate ______.
gains, gives.
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As the charge builds up, the potential difference increases. What does this allow electrons to do?
it allows them to travel to earth or a grounded objects when the difference is big enough.
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What do electric charges create?
Electric fields
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What is an electric field created around?
Any electrically charged object
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The closer you get to the field the ______ it is.
Stronger
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How can this be shown?
Using field lines
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The field lines go from ______ to ______.
+ve to -ve
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The field lines are always at what angle?
90
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What happens when the lines are closer?
The field is stronger
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What happens when you place a charged object in another object's field?
It will feel the force and, depending on their charge, the objects will either attract or repeal.
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What causes this?
The fields interacting with eachother.
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What causes the force to be stronger?
The stronger the field, the bigger the force.
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What causes a strong electric field between a charged and grounded oobjects?
A high potential difference.
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What does the strong field cause?
The electrons in the air particles to be ionised, making it a conductor ,and allowing current to flow
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Other cards in this set

Card 2

Front

What is current measured in?

Back

Amperes, A

Card 3

Front

Current will only flow in a _______ circuit...

Back

Preview of the front of card 3

Card 4

Front

...if there is _______.

Back

Preview of the front of card 4

Card 5

Front

What is potential difference?

Back

Preview of the front of card 5
View more cards

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