| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.41 |
| Score | 0% | 68% |
Why is an insulator a poor conductor of electricity?
an insulator has many free electrons |
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an insulator is made of inorganic material |
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an insulator is made of organic material |
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an insulator has few free electrons |
Insulators have valence shells that are more than half full of electrons and, as such, are tightly bound to the nucleus and difficult to move from one atom to another.
The formula specifying Ohm's law is which of the following?
V = IR |
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\(V = {I \over R}\) |
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\(V = {R \over I}\) |
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V = I2R |
Ohm's law specifies the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit: V = IR.
Direct current flows from the __________ terminal of the voltage source to the __________ terminal.
negative, negative |
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positive, positive |
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positive, negative |
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negative, positive |
Direct current flows in only one direction in a circuit, from the negative terminal of the voltage source to the positive. A common source of direct current (DC) is a battery.
This circuit component symbol represents a(n):
DC source |
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transistor |
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AC source |
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transformer |
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.
Capacitors store:
current |
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capacitance |
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resistance |
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electricity |
Capacitors store electricity and are used in circuits as temporary batteries. Capacitors are charged by DC current (AC current passes through a capacitor) and that stored charge can later be dissipated into the circuit as needed. Capacitors are often used to maintain power within a system when it is disconnected from its primary power source or to smooth out or filter voltage within a circuit.