Electricity Flashcards
What is Current?
the rate of flow of charge
What is a Coulomb?
the amount of charge that passes in 1second when the current is 1amp.
What is potential difference?
the energy per unit charge
What is Ohm’s Law?
The current through an ohmic conductor is directly proportional to the potential difference across it, provided the temperature is constant
What does the I/V graph look like for a metallic conductor?
a straight line, through the origin
What does the I/V graph look like for a filament lamp?
S curve, going through the origin
What does the I/V graph look like for a thermistor?
sinh(x) graph
What are semiconductors used for?
they are used in sensors
What is a thermistor?
a resistor with a resistance that depends on its temperature
What is the relationship between light intensity and resistance for an LDR?
the greater the intensity of light, the lower the resistance
what is the functions of a diode?
only lets current flow in one direction
What is the name of the direction in which a diode allows current?
forward bias
What is resistivity?
the resistance of a 1m length with 1m^2 cross sectional area
what is the equation for resistivity?
p= (RA)/L
what does resistance depend on?
-Length
-Area
-Resistivity
What is the key feature of a superconductor?
it has zero resistance
what is the problem with superconductors?
-needs to be kept at very cold temperatures
-hard and expensive to operate due to cold temperatures
What are the uses of superconductors?
-Power cables
- Strong electromagnets in medical equipment
-fast electric circuits
What is Power?
the rate of transfer of energy
Where does resistance come from?
electrons colliding with atoms
What is Internal Resistance?
resistance of the battery
What is Emf?
- Electromotive force
- the amount of electrical energy the battery produces for each coulomb of charge
what is terminal p.d?
the voltage across the cell when there is a current. i.e when there is internal resistance.
What is the equation for Emf?
E= V + Ir
what is the gradient and y-intercept of the V/I graph?
gradient: negative internal resistance
y-intercept: emf
What is Kirchhoff’s 1st Law?
the total current entering a junction = the total current leaving it
What is Kirchhoff’s 2nd Law?
The total emf around series circuit = the sum of the p.d.s across each component
What is a potential divider?
a circuit with a voltage source and a couple of resistors in series and the potential difference is divided in the ratio of the resistances
What is AC?
alternating current, current that changes with time
