Topic 3- Electricity Flashcards
What is charge?
Property of a particle, that can be positive or negative.
What is charge measured in?
Coulombs, C
What is the equation for current?
I = Q/t
Or
Current= Change in charge / Change in Time
What is the charge of an electron?
1.6x10^-19 coulombs
What is one coloumb defined as?
The amount of charge transferred by a current of 1 amp in one second.
What is drift velocity?
The average velocity of an electron in the direction of current.
The prefix ‘G’ means?
Giga (x1,000,000,000 or 10^9)
The prefix ‘k’ means?
Kilo ( x 1000 or 10^3 )
The prefix ‘m’ means?
Milli ( ÷ 1000 or 10^-3)
The prefix ‘μ’ means?
Micro (÷ 1,000,000 or 10^-6)
The prefix ‘n’ means?
Nano (÷1,000,000,000 or 10^-9)
The prefix ‘p’ means?
Pico (÷1,000,000,000,000 or 10^-12)
What is voltage?
A measure of the amount of energy a component transfers per unit charge.
What is the difference between electromotive force and potential difference?
E.M.F Supplies energy
P.D Uses energy
Sum of p.d and e.m.f is always….
Equal
(due to the conservation of energy)
What is an electron Volt?
1.6x10^-19
Charge of electron when passing through a p.d of one volt
What causes resistance?
Charge carriers (ie. electrons) colliding with lattice ions and being scattered.
Equation for resistance?
resistance = PD/current
What is Ohm’s Law?
Current through an (ohmic) conductor is directly proportional to the potential difference across it.
Providing temperature remains constant.
What does the IV graph look like for an ohmic conductor?
Positive linear graph
What is resistivity?
Property of a material, measuring its resisting power.
Equation for resistivity?
R=pl/A
How does increasing the cross-sectional area of a conductor affect its resistance?
The larger the cross-sectional area of a conductor, the lower its resistance, assuming all other factors remain the same.
How does it increasing the length of a conductor affect resistance?
The longer the conductor, the higher the resistance. Assuming all other factors stay the same.
What equation links the number of charge carriers in a metal, along with drift velocity, to the current flow?
I=nqvA
What is a semiconductor?
A component that can change its resistance based on external factors.
Give two examples of semi conductors and what they’re sensitive too.
- LDRs are sensitive to light
- Thermistors are sensitive to temperature
Describe how the resistance of a thermistor changes as the temp decreases
As the temp decreases, the resistance increases.
Describe how the resistance of an LDR changes as the light intensity increases.
As light intensity increases, resistance decreases.
How many loops can current take in a series circuit?
One
Does current differ at different points around a series circuit?
No
Does current differ at different points around a parallel circuit?
*Current splits at each point that it encounters a junction
*It splits in inverse proportion to the resistance along each path.
*The sum of all the currents on each path will add up to the original current from the battery.
This is due to the conservation of charge.
In parallel branches, what must the sum on voltages add up to?
They must be equal.
What rules does the conservation of energy cover in circuits?
*e.m.fs around a series circuit will add up, accounting for their directions.
*The sun of p.ds across components in a series circuit will be equal to the sum of e.m.fs
*In any parallel branches of a circuit, the sum of the voltages must be equal.
Resistors in series- derivation
Across resistors:
Vtot = V1 + V2+V3. (CoE)
As V=IR, and current is the same for all components around a circuit.
So:
IRtot= IR1+ IR2 +IR3. (CoC)
Rtot=R1+ R2 +R3
What is current?
Rate of flow of charge, per unit charge.
What’s the principle of charge conservation?
States that the total electric charge in a closed loop does not change.
What is Kirchoff’s first law?
The total current flowing into a junction is equal to the current flowing out of that junction.
Kirchoffs Second Law
The sum of the e.m.f.s is equal to the sum of the p.d.s in a closed loop (a form of conservation of energy).
What is Power defined as
The rate of energy transferred.
P=VI
What is internal resistance?
Caused by electrons colliding with atoms inside a battery, so energy is lost before electrons leave the battery.
