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| alloy iron core that carries coils of insulated wire to be revolved through the magnetic field |
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| the property that permits a circuit/device to store an electrical charge |
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| electrically non-conducting |
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| to provide a low impedence path. |
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| something that produces a flow of electricity |
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| a battery or other storage device (a potential charge of electricity at rest) |
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| highly magnetic/easily magnetized substance. ie: iron |
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| ability of a circuit/device to produce induction |
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| production of an electric current in a conductor by varying a magnetic field in its vicinity. |
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| total opposition to an alternating current presented by a circuit. (the sum of resistance, capacitance and inductance) |
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| something that persists in its state of rest or uniform motion until acted on by an external force |
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| atom/group of atoms that is positive or negatively charged (not neutral) |
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| to be totally or partially converted by ions |
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oppostion to an alternating current (caused by inductance and capacitance)
same as impedence but impedence also involves resistance |
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| opposition that a conductor offers to current (results from conversion of energy to heat/light etc) |
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| when the material has become fully magnetized |
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| in relation to welding power sources; the output of the machine when the load is constant. (the graph is created by applying a steady load and measuring the power source output response |
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| passage of electric current between two electrodes through a gas (ionized) |
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Definition
| Gas Metal Arc Welding (positive voltage is used) |
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Definition
| Gas Tungsten Arc Welding (when using this with direct current - negative voltage is applied) |
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| What is required to start an arc? |
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Definition
| Usually just touch the electrode to the work piece |
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| What is required to sustain arc? |
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Definition
| energy supplied from the power supply |
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| One method used by GTAW to initiate arc |
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Definition
| create an ionized column of gas by using very high voltage and low current |
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| The source of _________ must be designed in such a way that the requirements of the process are matched by its output. |
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Definition
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| The advantage of electronically controlled power sources is ... |
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| the ability to meet the needs of many different processes from one machine. |
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| Most large scale sources of electricity use _____________ |
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| Two ways voltage can be produced in electrical induction. |
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Definition
applying a changing magnetic field to a stationary conductor OR moving a conductor through a changing magnetic field.
**this is the essential difference between an alternator and a generator. |
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| Copper wire is a good conductor. T/F |
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| Flowing from positive...through circuit....to negative terminal |
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| Electrons flow from negative to positive terminals because they have a negative charge. T/F |
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from negative to positive.
arcs are analyzed as electron flow (NOT conventional current) |
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Definition
Current (I) = Volts (V) / Resistance (R)
OR
Volts (V) = Current (I) * Resistance (R) |
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Definition
| Resistance (R) = Volts (V) / Current (I) |
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| Ohm's Law applies to a welding arc. T/F |
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Definition
| False. Ohm's Law does NOT apply to a welding arc |
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| Titanium has high resistivity and is a poor conductor. T/F |
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Definition
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| The formula for Resistance in a welding arc... |
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Definition
| Resistance (R) = rl (resistivity/length) / A (cross sectional area in square meters) |
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| What is an advantage of Aluminum even though it has a higher resistivity than copper? |
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Definition
it is lighter.
(it has lower resistance per unity weight than copper) |
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| Electrical power is measured in _________ |
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Definition
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| Power is measured as a combination of the pressure (volts) and the flow rate of current (amperes) T/F |
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True
P = V (volts) * I (current) |
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| Electrical power is transformed into heat/light/motion depending on the device the current is flowing through. T/F |
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True.
ie: electricity flowing through a hair dryer produces heat. electricity flowing through a light bulb produces light. |
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| Energy is not created or destroyed, it simply changes from one form to another. T/F |
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Definition
True.
The conservation of energy law states that "...the total energy of an isolated system remains constand regardless of changes within the system. |
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| Kirchoff's voltage law states that around a circuit, voltages must add up to _______ |
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Definition
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| Kirchoff's current law states that current flow into any point in the circuit must be balanced by __________ |
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| What is a series circuit? |
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Definition
| A circuit with only a single path for current flow. |
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| In a series circuit, a resistor causes a voltage ________ (increase/decrease) as the current passes through. |
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Definition
decrease
(if thow resistors are in the series circuit, the current must be the same through each resistor...the sum of the voltage drops across the two must be equal to that from the source.) |
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Term
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Definition
| uses a single resistor with a sliding contact in the middle for a third connection...in essence, dividing the resistor into two resistors |
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| Variable resistors are often called potentiometers or pots because.... |
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Definition
| they vary the voltage or potential. |
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Term
| The _________________ provides a simple way of generating a variable voltage from a fixed voltage source. Such circuits are often used to provide a varying voltage signal to electrical equipment, the slider position being set by a knob on the control panel of the equipment. |
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Definition
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| to place a variable resistance in "series" with an electrical load....only one end of the variable resistor and the sliding connection are used. The current in the circuit is controlled by changing the total resistance in the circuit.....the variable resistor is called ______________ |
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Definition
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| The disadvantage of a rheostat circuit is... |
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Definition
| a lot of power is lost in the rheostat as heat |
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| circuits constructed to allow multiple current paths |
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| In parellel circuits, the currents must sum at the common points - the total current flowing must equal the sum of the currents passing through the two resistors. T/F |
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Definition
True
The total current flowing must equal the sum of the currents passing through the two resistors. |
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| Why is DC (direct current) voltage source not used at electric power plants? |
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| DC (such as in batteries) is more difficult to raise or lower than AC voltage. Power plants use alternating current (AC) where the current varies like a sine wave. |
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| In an AC circuit, current is positive as often as it is negative....the average current is __________ |
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Definition
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| The use of RMS (root mean square) amplitudes greatly simplies AC circuits because... |
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Definition
| they can be considered without reference to the sinusoidal nature of the waveform. - they can be analyzed in an equivalent manner to DC circuits |
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Term
| Any circuit which is capable of producing a magnetic flux has _______________ |
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Definition
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Term
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Definition
| changing magnetic flux induces a voltage (emf) that will oppose the change that produces it. |
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