[AS] Electricity Flashcards
Define current
The rate of flow of charge
What is the equation of charge?
I = (dQ)/(dt)
In what direction does current flow?
From + to -
Opposite from electron flow
Which direction do electrons flow?
- to +
Opposite from current flow
What is the unit of charge?
The coulomb
How is a coulomb defined?
The amount of charge that passes in one second when the current is 1A
How do you attach an ammeter in a circuit?
In series
What is the elementary charge, e?
1.60 x 10^-19
Define potential difference
Work done per unit charge
Work done by a coulomb of charge to pass between two points
What is the equation for voltage with work done and charge?
V = W/Q
What carries charge in liquids and gases?
Ions
What is the equation for kinetic energy?
½mv^2
Define mean drift velocity
Average velocity of the charge carriers
What is an ohmic conductor?
Ohmic conductors have a constant Resistance
What 3 things determine resistance?
Length, area and resistivity
What resistivity do superconductors have?
Zero
How do you make a metal a superconductor?
Cool them down
Define power
Rate of transfer of energy
Why do things have resistance?
Electrons collide with atoms and lose energy to other forms
What is internal resistance?
Resistance inside batteries which causes their cells to heat up
What is emf?
The amount of electrical energy the battery produces for each coulomb of charge
What is external resistance?
The total resistance of all components in the external circuit
What is terminal p.d?
The energy transferred when one coulomb of charge flows through the external resistance
What are the equations for emf that to use not given in the formula book?
Emf = V + v
V = (emf) - Ir
