Electronic Principles
Which one of the following principles best describes the basic operation of an electromagnet?

Current flowing through a conductor generates a magnetic field
Like magnetic poles attract, while unlike poles repel
None of these
Like magnetic poles repel, while unlike poles attract
Current is induced in a conductor that is moving through a magnetic field

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Electronic Principles
In a pure inductor:

ac current leads the voltage by 90 degree
ac current lags the voltage by 90 degree
None of these
ac current and voltage are exactly in phase
ac current is converted to dc voltage

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Electronic Principles
What is the primary difference between primary and secondary cell batteries?

Secondary-cell batteries can be recharged and used many times, whereas primary-cell batteries cannot be properly recharged
Primary-cell batteries must be recharged at a much slower rate that secondary-cell batteries
Primary-cell batteries can be recharged and used many times, whereas secondary-cell batteries cannot be properly recharged
Primary-cell batteries use chemical cells, whereas secondary-cell batteries use an alternative energy source, such as thermal or magnetic energy, to supplement their outputs
None of these

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