Electricity Flashcards
(29 cards)
You are given current and time, what formula do you use to find the charge
I = Q/t
How do you find the voltage when given energy and charges
V=E/Q
How do you find resistance when given voltage and current
V=RI
What formula relates resistance to length and area
R =Pl/a
What formula links power and voltage
P=VI
What’s the standard formula to find power?
P=E/t
How do you find the total resistance in a Series circuit
R = R1 + R2…
How do you find the voltage used for each device in a series circuit
Use ratio method based on the resistance of the devices
Will the devices in a series circuit still work if one of them isn’t working?
No
Is voltage shared in a series circuit
Yes
Is voltage shared in a parallel circuit
No
How do you find the total current in a parallel circuit
I = I1 + I2…
How do you find total resistance in a parallel circuit
R = 1/R1 + 1/R2…
What determines whether a transformer is a step up or step down transformer
The number of coils on the output side - if less, it’s step down, if more, it’s step up
State the two formulas used for transformers
VpIp = VsIs Ns/Np = Vs/Vp
Define the left hand rule
Thumb, Force
Pointer, Magnetic Field
Middle finger, Current
Define electromagnetic induction
When a current is induced due to the change of a magnetic field close to a solenoid
What device uses the left hand rule
Motor
What devices use electromagnetic induction
Generator and Transformers
In which direction does conventional current flow
From positive to negative
what is a resistor
a device used to provide resistance to reduce currents or keep them at a constant level
what is a variable resistor or rheostat
used for varying currents in devices to do things such as increasing or decreasing brightness or volume
define a thermistor
a device which has high resistance when it’s cold, but low resistance when it’s hot
what is a light dependent resistor or LDR
a device with high resistance in the dark but low resistance in the light. used for automatic lights
