9. Electricity Flashcards
Define electric current-
- units its measured in
Electric current is the flow of charge carriers.
Measured in amperes (A) or amps
Define electron flow and conventional current
Electron flow is the flow of electrons from negative terminal to positive terminal in electric wires.
Conventional current is the flow of positive charge from positive terminal to negative terminal.
Device used to measure the current and correct way to attach it in the circuit.
Device- ammeter
Ammeter should be connected in series to measure the current around the circuit
Explain quantisation of charge-
The charge-on-charge carriers (protons, electrons or ions) are quantised.
The charge comes in definite bits- a single proton having a single positive charge and a single electron having a single negative charge.
In this way, the quantity of charge can be quantised based on how many protons or electrons are present; positive and negative charge has a definite ‘minimum magnitude’ and always comes in the multiple of this magnitude. (This means that if we say something has a given charge, the charge is always a multiple of the charge of an electron by convention).
hence- the magnitude of charge is known as an elementary charge.
Define elementary charge and its value-
The magnitude of the charge is known as the elementary charge.
e= 1.60 × 10 to the power -19 C
; denoted by e.
protons (+vely charged) = +e
electrons (-vely charged) = -e
Ions= +e and -e
How do we calculate electric charge-
electric charge measured in coulombs (C)-
Q = It
Q= charge - C
I= current - A
t= time - s
the equation for calculating current in conductors-
I = A n v q
I = current - A
A = cross-sectional area- m2
n= no of the density of charge carriers (no of charge carriers per unit volume) - m-3
v = drift speed of charge carriers - ms-1
q = charge of each charge carrier - C
Define potential difference
energy transfer per unit charge flowing from one point to another.
measure in volts (V)
1volt = Joule per coulomb (J C-1)
Which device is used to measure the potential difference
The potential difference or voltage is measured using a voltmeter.
The voltmeter should always be connected parallel to the component you are measuring the potential difference of.
The equation used to calculate the potential difference
V = W / Q
V = potential difference- volts
W = work done- joules
Q = charge- coulombs
What is power and its three equations-
Power is the rate of doing work. The power produced by an electrical device-
p = power (watts)
I = current (Amps)
V= potential difference / voltage (volts)
R= resistance (ohms)
1. P = IV
2. P = I2 x R
3. P =V2/ R
Define resistance
Resistance is defined as the opposition of the current.
measure in ohms
higher the resistance, lower the current.
as V= IR
R= V/I
What is ohm’s law-
Ohm’s law states that for a conductor at a constant temperature, the current through it is proportional to the potential difference across it.
CONSTANT TEMPERATURE = CONSTANT RESISTANCE
eq:
V=IR
