Voltage, Current & Resistance
Kilohm
1.000 ohms. Usually written 1k omega.
Megohm
1.000.000 ohms. Written 1M omega or 1 meg omega.
Open circuit
A circuit with a break or open path that stops current flow.
Closed circuit
A complete path allowing current to flow.
Insulator
A material that does not give up free electrons easily and offers opposition to current flow.
Conductor
A material that gives up free electrons and offers only slight opposition to current flow.
Ohmmeter
A meter for directly measuring the resistive component of an electrical circuit.
Voltmeter
A meter that is connected across the line to measure the potential difference (voltage) between two points.
Ammeter
A meter used to measure electric current. It is connected as part of a circuit.
High Voltage
A term that normally implies a voltage higher than 600 volts.
Current in an electric circuit is measured with an instrument called an _____.
AMMETER
The instrument that measure electrical current is the...
AMMETER
How should a voltmeter be connected in a circuit to measure voltage?
Across or in parallel with the potential points being measured.
An ammeter must be connected in the circuit in such a way that...
All current flows through it.
Megohmmeter
An insulation-resistance tester. Consisting of a high-range ohmmeter and a high-voltage generator.
In an electrical system, the potential is provided by a storage _____, a mechanically driven _____, or a dry cell.
BATTERY; GENERATOR
When current is measured, the ammeter is connected so that it becomes part of the _____.
CIRCUIT
When two points that have an electrical potential difference are joined by a conductor, _____ _____ results.
CURRENT FLOW
(I) means?
Current, Amp or Amperage
According to Ohm's Law, the current in any circuit is _____ proportional to the applied voltage.
DIRECTLY
When the current (I) and resistance (R) are known, the voltage (E) can be found by the formula.
E = I x R
An electrical current is produced when an applied voltage sets the free _____ of a material in motion.
ELECTRONS
Free Electrons
Electrons in the outer orbits of an atom that can easily be forced out of their orbits.
Without a given potential, how do free electrons in a conductor constantly move?
From negative to positive.
Which of the following provides the electrical potential for an electrical system.
GENERATOR
Omega
Greek letter for ohm.
Materials that have few free electrons are called _____.
INSULATORS: Mica, porcelain, glass, bakelite and silicone are good insulating materials.
Current moves through a conductor at the speed of _____.
LIGHT: Approximately 186,000 miles per second.
What two meters are used to measure electrical resistance?
MEGOHMMETER & OHMMETER
The unit for measuring circuit resistance is the...
OHM
The law that defines the relationship between current, voltage and resistance is called _____ Law.
OHM'S LAW: If any two electrical characteristics are known, you can determine the third with Ohm's Law.
The resistance of a conductor is measured in a unit called...
OHM: Named after the German physicist and mathematician George Simon Ohm.
Two meters that can measure electrical resistance are the _____ and _____.
OHMMETER & MEGOHMMETER: The ohmmeter measures circuit resistance; the megohmmeter measures the high resistance of insulation.
(R) means?
Ohms or Resistance
When you connect a D-C ammeter into a circuit you should always observe the correct _____.
POLARITY
If a battery is connected to teh two ends of a wire, the electrons movement in the wire is toward the _____ battery terminal.
POSITIVE
What term besides voltage is used to indicate electrical pressure?
POTENTIAL
The terms voltage and potential are both used to indicate the electrical _____ in a system.
PRESSURE
(P) or (W) means?
Power
The opposition to current flow in an electrical circuit is called _____.
RESISTANCE
Ohm
The basic unit of resistance measure. One ohm is equal to the resistance that allows 1 ampere of current to flow when an emf of 1 volt is applied.
Electron Current
The current from a negative charge to a positive charge.
Electromotive Force (emf)
The force that causes electrons to move through a conductor.
Current
The movement of free electrons in a material.
Resistance
The property of a circuit which limits, opposes or resists the flow of electricity through it.
Voltage
The term most frequently used to express the difference of potential between two charges or between two points of a circuit.
Ampere
The unit of measurement of electric current. One ampere is one coulomb per second.
The electron movement along the conductor of a circuit is the same everywhere, provided the applied _____ remains constant.
VOLTAGE
Ohm's Law is used to determine relationships between...
VOLTAGE, CURRENT & RESISTANCE
The instrument used to measure difference in electrical potential is called a _____.
VOLTMETER
To measure electrical potential, you should use a/an...
VOLTMETER
(V) or (E) means?
Voltage
