Electric Circuits Flashcards
What is the electric current (I)
The rate of flow of charged particles
What is the equation for the electric current?
I = ∆Q/ ∆t
What is voltage?
1 volt -> potential difference between two points when 1 joule of work is done to move a charge of 1 coulomb.
What’s the equation for voltage?
V = W/ Q
what is the electric current’s SI unit
Ampere
what is the solid definition of Ampere (A)?
The current flowing in two parallel wires 1m apart in a vacuum such that there is an attractive force of 2 * 10^7 N per meter length between them
what is 1 Ampere equal to
1 ampere -> 1 Coulomb of charge passing a point in 1 second
In what direction does the conventional charge flow?
From positive to negative
In what direction do the electrons flow in a circuit?
From negative to positive
What device do we use to measure the current?
The ammeter
how do we use the ammeter
It goes in series with the other parts of the circuit
what is the mass of an electron?
9.1 * 10^-31 kg
what is elementary charge equal to?
1.6 * 10^ -19 Coulomb
What is the definition of a coulomb
The charge that flows past a point in 1 second when there is a current of 1 amp
What is the equation for the charge?
∆Q = I * ∆t
What is Kirchhoff’s 1st Law?
at any point in an electrical circuit, the sum of currents into that point is equal to the sum of currents out, electrical charge is conserved.
what is the cross-sectional area equal to?
A = π d^2 / 4
what is the volume equal to
V = Length * Area
what is the equation for the no. of free electrons
volume * charge density | nL A
Total charge free to move =
= nLAe
Time for charge to leave this bit of wire =
= length / drift velocity
Another derivation of I = Q / T is
I = n A v e
what is the velocity equal to
v = n A e / I
what is the electro-motive force
EMF is the energy per unit charge transferred from chemical energy into electrical energy
what tool do you use to calculate the potential difference in a circuit?
A Voltmeter
what does the voltmeter need to have?
High resistance
what is the difference between a voltmeter and an ammeter?
A voltmeter measures the electrical potential across that component, an ammeter measures goes in series and measures the current through a position
What’s the difference between emf and potential difference?
both measures in volt, but EMF is the energy per unit charge transferred from chemical to electrical, potential difference is the energy per unit charge transferred from electrical into other forms
what is the potential difference?
the energy per unit charge transferred from electrical into other forms
what is the voltage equal to
v = IR
The relation ship between voltage and current is
Directly proportional
The relationship between current and resistance is
Inversely proportional
Ohm’s Law states that
Ohm’s law states that electric current through a conductor between two points is directly proportional to the voltage across the two points.
kirchhoff’s 2nd law states that
As you go around a voltage in. a loop the total voltage = 0
