| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.48 |
| Score | 0% | 70% |
A capacitor is often used for which of the following purposes?
to convert alternating current into direct current |
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to allow a small amount of current to control a large amount of current |
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as a primary power source |
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to maintain power in a circuit when the primary power source is disconnected |
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.
Voltage and current are __________ proportional.
indirectly |
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inversely |
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not |
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directly |
Voltage (V) is the electrical potential difference between two points. Electrons will flow as current from areas of high potential (concentration of electrons) to areas of low potential. Voltage and current are directly proportional in that the higher the voltage applied to a conductor the higher the current that will result.
If an electrical circuit is interrupted, which of the following will result?
short circuit |
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open circuit |
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closed circuit |
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parallel circuit |
A closed circuit is a complete loop or path that electricity follows. It consists of a source of voltage, a load, and connective conductors. If the circuit is interrupted, if a wire is disconnected or cut for example, it becomes an open circuit and no electricity will flow.
Which of the following statements about a capacitor is false?
a capacitor remains charged even after the input voltage is removed |
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it is safe to touch a capacitor with your hands as long as it is small |
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you should always discharge any capacitors before working on an electronic circuit |
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to discharge a capacitor safely, use a high-wattage resistor comparable to the capacitance of the capacitor |
The purpose of a capacitor is to retain electric charge and it will do so even after its input voltage is removed. After the input voltage is removed, the capacitor will slowly discharge but, depending on the size and characteristics of the capacitor, discharging could take from a few minutes to a few years. So, it's never safe to touch a capacitor with your hands and you should make sure to discharge any capacitors in a circuit before working on it using an appropriately high-wattage resistor or a capacitor discharge tool.
The formula specifying Ohm's law is which of the following?
V = I2R |
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V = IR |
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\(V = {I \over R}\) |
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\(V = {R \over I}\) |
Ohm's law specifies the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit: V = IR.