| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.24 |
| Score | 0% | 65% |
Silver and gold are among the most highly conductive elements. Why is copper used much more often as a conductor in electrical circuits?
silver and gold are costly |
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copper is durable and relatively cheap |
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all of these |
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silver and gold are brittle |
All conductors have resistance and the amount of resistance varies with the element. But, resistance isn't the only consideration when choosing a conductor as the most highly conductive elements like silver and gold are also more expensive and more brittle than slightly less conductive elements like copper. A balance needs to be struck between the electrical qualities of a material and its cost and durability.
Which of the following will increase the magnetic field produced by the electric current in a wire?
construct the wire from conductive material |
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wind the wire into a coil |
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construct the wire from insulative material |
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wrap the wire around a ceramic core |
A moving electric current produces a magnetic field proportional to the amount of current flow. This magnetic field can be made stronger by winding the wire into a coil and further enhanced if done around an iron containing (ferrous) core.
Alternating current changes __________ many times each second.
direction |
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period |
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frequency |
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resistance |
In contrast to the constant one-way flow of direct current, alternating current changes direction many times each second. Electricity is delivered from power stations to customers as AC because it provides a more efficient way to transport electricity over long distances.
Inductance is a factor in which of the following?
a DC circuit |
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batteries connected in serial |
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an AC circuit |
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determining energy stored by a capacitor |
Inductance is a property of an AC circuit (or a component in an AC circuit) that quantifies resistance to changes in current. The current in an AC circuit is continuously changing and inductive reactance (the opposition to change) depends both on the inductance of the circuit or component and the rate at which the current is changing.
This circuit component symbol represents a(n):
resistor |
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inductor |
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capacitor |
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transformer |
An inductor is coiled wire that stores electric energy in the form of magnetic energy and resists changes in the electric current flowing through it. If current is increasing, the inductor produces a voltage that slows the increase and, if current is decreasing, the magnetic energy in the coil opposes the decrease to keep the current flowing longer. In contrast to capacitors, inductors allow DC to pass easily but resist the flow of AC.