Studied by 84 peopleCurrent
The continuous flow of charge
Average current
Iavg = change in charge/ change in time
Battery
A battery is a device that maintains an electric potential difference between the two terminals.
Direct current
The flow is from higher potential to lower potential. The electricity also flows in that direction called direct current.
Resistance
It is the impedance to the flow of electricity through a material. Asa charge moves through a material, it eventually hits a non-moving nucleus in the material.
Resistivity
It can be thought of as the density of nuclei the electrons may strike.
R = ρ l / A
R = resistance of the circuit
ρ = resistivity
l = length
A = cross-sectional area
low resistivity
conductors
high resistivity
insulators
resistors in series
R eq = R1 + R2
resistors in parallel
1/Req = 1/R1 + 1/R2
Ammeter
An ammeter is a device with a very low resistance that measures the current.
Voltmeter
It measures the electric potential called potential drop.
Ohm’s Law
V = IR
R is the resistance in the circuit.
V is the potential difference in the circuit
I is the electric current
Power dissipation
P = VIP = I^2 RP = V^2 IR
P is the power
V is the potential difference in the circuit.
I is the electric current.
Kirchhoff’s rules
The loop rule states that the voltage drop across any complete loop in the circuit is 0V.
This statement follows from the conservation of energy when applied to circuits.
The junction rule states that the sum of all current flowing into any junction is equal to the current flowing out of the junction.
This statement follows from the conservation of charge.
Capacitance
C = QV
C = refers to the capacitance that we measure in farads
Q = refers to the equal charge that we measure in coulombs
V = refers to the voltage that we measure in volts
Besides, there is another formula that appears like this:
C = kε0Ad
C = refers to the capacitance
K = refers to the relative permittivity
ε0 = refers to the permittivity of free space
A = refers to the surface area of the plates
d = refers to the distance between places measured
Capacitors in parallel
Cp = C1 + C2
Capacitors in series
1/Cs = 1/C1 + 1/C2
Name three possible energy sources for a circuit
Battery
Photoelectric cell
Generator
A circuit is opened and closed using a:
Switch
What will happen to the charges in a circuit when a switch is closed?
The charges will flow through the circuit.
What will happen to the charges in a circuit when a switch is open?
The circuit is broken and the charges stop flowing through the circuit.
What is the standard voltage per branch in a home in the United States?
120 V
A switch that automatically opens if the current is too high is a ________________
Circuit Breaker
The symbol used to represent resistance in a schematic diagram is
a zigzag line
A closed circuit is a circuit in which charge
can flow
When two light bulbs are connected in series, the
same amount of current always flows through each bulb
When resistors are put in parallel with each other their overall resistance is
smaller than the resistance of any of the resistors
As more lamps are put into a series circuit, the overall current in the circuit
decreases
As more lamps are put into a parallel circuit, the overall current in the circuit
increases
When one light bulb in a parallel circuit containing several light bulbs burns out, the other light bulbs
burn the same as before
Electrical devices in our homes are connected in
parallel
Note
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