Section 6: Electricity Flashcards
What is ohm’s law?
The current through an ohmic conductor is directly proportional to the potential difference across it.
How do you make a super conductor?
cool some materials below a critical temprature called the transitional temprature.
What are the uses of super conductors?
-power cables that transmit electricity without any loss of power
-Realy strong electromagnets , medicine
-fast electronic circuits
Difine power.
the rate of transfer of energy
What is Kirchhoff’s first law?
the total current entering a junction= the total current leaving it
What is kirchhoff’s second law?
the total e.m.f around a series circut= the sum of the p.ds across each component
The temprature of a therimistor is decresed
Stater the changes to the ammerter resistance and voltmeter readings.
Ameater reading - decreases
voltmeater- increases
resistance - increases
What is a rheostat?
Variable resistor
What is the equation for potential dividers?
V in /R1 +R2= V out / R2
v out = v in (r2/r1 + r2)
For a component that obeys ohms law, What would you see on a power current graph?
an positive exponential curve
What is a potential divider?
A combination of resistors in series connected across a voltage source. There is a split pd.
A potential divider with a variable resistor and a thermistor is set up. There is a voltmeater across the thermistor.
The resistance of a variable resistor is increased, What happens to the volt meater reading?
The resistance increases.
The pd across the variable resistor increasses.
The dp across R + Pd across T = supply pd/voltage.
so the pd across the thermistor decreases.
A battery has an emf of 5.30V and a negligible internal resistance.
What is meant by emf?
The amount of energy transfered from chemical enegy to eletrical energy.
5.30 j of energy per coulomb of charge. V=W/Q
Explain why in a filiment lamp increase of current increases resistance.
-As current increases, the resistance increasess
-The temprature increasing also increases the lattice vibrations
-The more lattice vibrations, the more frequent the collisions hence higher resistance
Electromotive Force:
The amount of energy transferred by a source, to each unit of charge that passes through it.
