ELEC-256 [1-6] Flashcards
Basic Circuit - Pictorial representation
Basic Circuit - Schematic Representation
One to four valance electrons
Conductors
Semiconductors
Five Valance Electrons
More than Five Valance Electrons
Insulators
The long bar denotes the _______ and the short bar ______
- Positive Terminal
- Negative Terminal
Symbol for a cell
Symbol for a battery
A 1.5 volt battery
When the amount of charge that passes a point in one second is one coulomb, the current is
One Ampere
Voltmeter
Ammeter
Cells in series
Cells in Parallel
Describe
Measuring Voltage
- To measure voltage place the voltmeter leads across the component whose voltage you wish to determine.
Measuring current
- To measure current, insert the ammeter into the circuit so that the current you wish to measure passes trough the instrument
Open circuit
Closed circuit
Using a fuse to protect a circuit
Basic Resistive Circuit
Resistance
Is an opposition to current flow. It can be thought of as friction in the circuit. Resistance is measure in Ohms
Ohm’s law
For a fixed resistance Ohm found that doubling the voltage____
Doubled the current
For a fixed voltage Ohm found that the opposition to current was
directly proportional to the lenght of the wire and inversely proportional to its cross-sectional area
Ohms was able to show that current is inversely proportional to
resistance e.g when he double the resistance he found that the current decreased to half of its former value
The resistance of a material is dependent on:
- Type of material
- Lenght of the conductor
- Cross-Sectional area
- Temperature
The resistance of a metallic conductor is inversely proportional to the …
Cross sectional area of the conductor
- p=resistivity, in ohm meters
- l=lenght in meters
- A=across-sectional area in square meters
If the diameter of a wire is doubled, its resistance will be…
One-fourth as great
Any material for which resistance increases as temperature increases is said to have a…
positive temperature coefficient
Types of resistors
- Fixed resistors (constant resistance values)
- Variable resistors (potentiometers and rheostats)
Defined as the rate of doing work
Power
Defined as work per unit charge
voltage
The rate of transfer of charge
current
Formulas for Power
Defined as the ratio of power output Pout to power input Pin usually expressed in percent and the noted by the greek letter Π (eta)
Efficiency of a device or system
is the combination of any number of sources and loads connected in any manner that allows charge to flow
An Electric Circuit
All electric circuits obtain their energy either from …
a direct current (dc) source or from an alternating current (ac) source
What two conditions determine whether two elements are connected in series?
Two elements are said to be in series if they are connected at a single point and if there are no other current-carrying connections at this point.
The summation of voltage rises and voltage drops around a closed loop is equal to zero
Kirchhoff’s voltage law
Is defined as any path that originates at a point, travels around a circuit, and returns to the original point without retracing any segments
A closed loop
If a circuit has more than one voltage source in series then the voltage sources may effectively be replaced by…
A single source having a value that is the sum or difference of the individual sources
Voltage Polarities
When voltage sources do not result in voltage rises in the same direction
A typical lead-acid automobile battery consists of six cells connected in series. If the voltage between the battery terminals is measured to be 13.6 V, what is the average voltage of each cell within the battery?
Interchanging series components
The order of series components may be changed without affecting the operation of the circuit.
The voltage dropped across any series resistor is proportional to the magnitude of the resistor. The total voltage dropped across all resistors must equal the applied voltage source(s) by KVL.
The Voltage Divider Rule
If the output terminals are shorted together, the current in the circuit will be a maximum and the terminal voltage will be equal to approximately zero.
In such a situation, the voltage dropped across the internal resistance will be equal to the voltage of the ideal source.
Terminal Voltage
The voltage that appears between the positive and negative terminals
Simplify the circuit shown below into a single source in series with the four resistors. Determine the direction and magnitude of the current in the resulting circuit.
An “arbitrary electrical point of reference” or “common point” in a circuit
Circuit Ground
If an ammeter having an internal resistance of 250 Ω is used to measure the current in the circuits, determine the current through the ammeter and calculate the loading effect for each circuit
Kirchhoff’s Current Law (KCL)
The summation of currents entering a node is equal to the summation of currents leaving the node.
Verify that Kirchhoff’s current law applies
3 mA + 6 mA + 1mA = 2 mA + 4 mA + 4 mA
Determine the unknown currents
An important effect of combining parallel resistors is that the resultant resistance will always be …
smaller than the smallest resistor in the combination.
Solve for the total conductance and total equivalent resistance
Determine the conductance and resistance of the network
