Electricity Flashcards
(28 cards)
What is a conductor? What is a good conductor and why?
Materials that allow the flow of electric charge. Metals are good conductors as the delocalized electrons are free to flow through the metal and so carry a current.
What is a insulator? What is a good insulator and why?
Materials that do not allow the flow of electric charge. Plastic is a good insulator as it does not contain free electrons and so current is unable to flow.
How do metals conduct electricity ?
The delocalized electrons involved in metallic bonding allow metals to conduct electricity
What is an electric current and what are the 4 things needed for one to work?
A path for electric charge to flow along
-A source of energy
-A complete loop
-A component
-No short circuits
Why do cables have plastic coatings?
Metals usually copper are used to make electrical wires because they conduct current, to prevent electrical shocks the metal wires are coated with a thick layer of plastic
What is conventional current?
Positively charged particles moving from the positive terminal around a circuit to the negative terminal
What is electron flow?
Charge carried by electrons, flowing from the negative terminal to the positive terminal
In a series circuit if the circuit is broken anywhere, what will happen?
The current will not flow
What are the nine circuit diagrams you need to know ?
Switch Cell. Battery
Resistor Variable Resistor Lamp
Voltmeter Ammeter. Fuse
What is a series circuit?
One in which the components are arranged one after another
What is cell polarity?
Is concerned with which end of a cell is positive and which end is negative, see figure 9.2 and 9.3
What is the equation for charge? (Symbol, word and measured in)
Q = I x t
Charge = current x time
Charge - Coulombs (C)
Current - Amperes (A)
Time - Seconds (s)
What is ohms law?
That the current in a metallic conductor is directly proportional to the voltage across its ends provided the temperature remains constant
How do you ensure the wire’s temperature remains constant in an experiment
-keeping the voltage low (current remains small)
-switching off the current between readings to allow the wire to cool
Summary for an VI Graph
V ^ m=R
| / High resistance = large m
| / Low resistance = small m
| /
| /
|/_____________>
I
Summary of an IV graph
V ^ m=I/R
| / High resistance = small m
| / Low resistance = large m
| /
| /
|/_____________>
I
What is an ohmic conductor
-Is one in which the potential difference is directly proportional to the current passing through it
-provided the material is maintained at a constant temperature
What is the equation for voltage? (Symbol, word and measured in)
V = I x R
Voltage = current x resistance
Voltage - volts/V
Current- Amps/A
Resistance - Ohms/(~)
Practical for a filament bulb
Current in a series circuit is? Voltage in a series circuit is?
The current flowing through a series circuit is the same everywhere
Voltage of the supply is equal to the sum of the voltages across the separate components in a series circuit. (Ein = Eout hence supply voltage = V1 + V2 + V3 etc)
Voltage in a parallel circuit is? Current in a parallel circuit is ?
The voltage across each component in a parallel circuit is the same as
that of the supply( 1/Rt = 1/R1 + 1/R2 + 1/R3 etc )
The total current taken from the supply is the sum of the currents through the separate components in a parallel circuit.
Resistance and length Graph. What are the results?
The graph is a straight line that passes through the origin; and
- this shows that for a metal wire at constant temperature the resistance and length of wire are proportional
Graph of resistance against CSA equation? (Symbol, word and measured in)
R = k x L
Resistance = Resistance x Length
Resistance = Ohms/ (~)
Resistance = ohms/meter (~)/m
Length- Metres/m
The resistance of a piece of wire depends on several factors. What are these factors?(summary)
