| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.43 |
| Score | 0% | 69% |
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 brittle |
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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 costly |
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.
The valence shell of a semiconductor is how full of electrons?
more than half full |
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half full |
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empty |
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less than half full |
Semiconductors have valence shells that are exacly half full and can conduct electricity under some conditions but not others. This property makes them useful for the control of electrical current.
Why does current in an electric circuit create heat?
the wire in the circuit burns when current passes through |
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current is naturally hot |
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heat is created when the current overcomes resistance in the wire |
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voltage is naturally hot |
Current in an electric circuit creates heat when the current overcomes resistance in the wire.
A __________ electric current produces a magnetic field proportional to the amount of current flow.
stationary |
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high voltage |
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moving |
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low voltage |
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.
The voltage output of a transformer primarily depends on which of the following?
the diameter of the wire in the coils |
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the conductor used for the wire in the coils |
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the number of turns in the wire of the coils |
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the diameter of the coils |
A transformer utilizes an inductor to increase or decrease the voltage in a circuit. AC flowing in a coil wrapped around an iron core magnetizes the core causing it to produce a magnetic field. This magnetic field generates a voltage in a nearby coil of wire and, depending on the number of turns in the wire of the primary (source) and secondary coils and their proximity, voltage is induced in the secondary coil.