Circutis Flashcards
Current
Movement of positive charge through a conductive material over time and is given is Amperes (C/S)
Voltage
Potential difference between two points and is given in volts (J/C)
Electromotive force (emf)
Potential difference of the voltage source for a circuit, usually a battery and is given in volts
Conductivity
The reciprocal of resistance and is a measure of permissiveness to current flow, measured in siemens (S)
Ohm’s Law
For a given resistance, the magnitude of the current through a resistor is proportional to the voltage drop across the resistors
Kirchhoff’s Current Law
Kirchhoff’s Current Law says that the sum of all currents flowing into a node equals the sum of currents flowing out of the node.
Kirchhoff’s Voltage Law
The sum of voltages around a loop is zero.
- You can trace a loop starting from any node. Walk around the loop and end up back at the starting node, the sum of voltages around the loop adds up to zero.
- You can go around the loop in either direction, clockwise or counterclockwise. Kirchhoff’s Voltage Law still holds.
- If a circuit has multiple loops, Kirchhoff’s Voltage Law is true for every loop.
How does adding or removing a resistor change the total resistance of a circuit with resistors in series? In parallel?
Adding a resistor in series increases the total resistance of a circuit; removing one in series decreases the total resistance in the circuit
Adding a resistor decreases resistance in parallel, while removing one increases it.
What four physical quantities determine the resistance of a resistor?
Resistivity, length, cross sectional area, and temperature
How does power relate to current, voltage and resistance
P= IV= I^2R= (V^2/R)
What does internal resistance of a battery do?
It lowers the available voltage for the circuit and thus lower the current for any given resistance.
What happens when you put a non-conducting material (dielectric material) between the two plates?
Capacitance increases
How does a dielectric in isolated capacitors Increase the capacitance?
Reduce the voltage
Capacitance equation
C= Q/V
Units for capacitance
Farad (1F= 1C/V)
Uniform electric field between plates equation
E=V/d
Potential energy stored in capacitance
U= 1/2CV^2 or qV/2
Capacitance due to dielectric material
C(new)= kC
How does the capacitance increase in a dielectrics in circuit capacitors?
By increasing the amount of charge by a factor of dielectric constant and voltage constant because battery is there so wants to maintain a constant voltage.
Capacitors in a series
Total capacitance decreases
1/Cs= (1/C1 + 1/C2 + 1/C3…)
Charge same on each capacitor
Voltage is sum of individual capacitors
Capacitors in parallel
Total capacitance increases Cp= C1 +C2 +C3 +Cn.... Voltage same across each capacitor Same voltage at each capacitor as the battery Greater capacitance= greater charge
How does a dielectric affect capacitance, voltage and charge
A dielectric will increase capacitance. If the capacitor is isolated, its voltage will decrease when a dielectric is introduced
If its in a circuit, its voltage is constant because it is dictated by its voltage source.
If the capacitor is isolated, the stored charge will remain constant and if its in a circuit the stored charge will increase.
How does adding or removing a capacitor in series and parallel affect capacitance?
Adding a capacitor in a series decreases the total capacitance of a circuit; removing one in a series increases the total capacitance in the circuit
In parallel, adding a capacitor increases capacitance and removing it decreases it.
What physical qualities contribute to the capacitance of a capacitor?
Surface area, distance, and dielectric constant all contribute to the capacitance of a capacitor.
Ammeter
Measures:Current
Placement: In series
Ideal resistance: 0
Need circuit to be on
Voltmeter
Measures: Voltage
Placement: Parallel
Ideal resistance: Infinite
Need circuit to be on
Ohmmeter
Measures:Resistance
Placement: Two points in series with circuit
Ideal resistance: 0
Does NOT Need circuit to be on
Resistors generate
Power
