Chapter 5 - Electricity and Magnetism Flashcards
What is conventional current?
It’s a current that flows from positive to negative.
What are conduction electrons?
They are negative electrons that flow the opposite way than conventional current does in a circuit.
Why does the metal wires heat up in a circuit?
As the conduction electrons move the interaction between them and the lattice ions means work is done, so when the current flows the metal heats up.
What is drift velocity?
The speed of the electrons due to the current.
What’s the equation to calculate the electrical conduction?
I = nAvq n = number of density of the charge-carries (the number per unit volume that are available to move) q = the charge on each carrier v = average speed
What is current and its units?
Rate of flow of electrical charge
1A = 1Cs^-1
1As = 1C
What is an ohmic material?
If current and potential difference are proportional
What’s Ohm’s law?
The current flowing through a piece of metal is proportional to the potential difference across is providing that temperature remains constant.
What’s a resistor?
A device with constant resistance. (Aka an ohmic device)
What’s resistance?
The mathematical ratio between potential difference and current:
Potential difference/ current
1 ohm = 1VA ^ -1
What would you need for a current to flow if something had a high resistance?
A large potential difference
What are the three equations for power?
p = V x I p = I^2 x R p = V^2 / R
What’s the first conversation law?
The conversation of charge (it’s never created or destroyed only transformed)
The sum of I = 0 (junction)
Current flowing in a junction is the same as the current flowing out.
What’s the second conservation law?
The conservation of energy.
Sum of voltage = zero (loop)
Around any loop total energy per unit charge must sum zero.
What happens if the chosen loop direction is from the negative side of the battery to its positive side?
It’s an increase in pd and the value is positive when calculating the sum