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Questions and Answers
What is the equivalent expression of tan x cot x – cos2 x?
Which light bulb rated at 40 watts, 60 watts, and 150 watts will use electrical energy the fastest?
What is the basic unit of electrical power?
Which two electrical units multiplied together give the unit 'watts'?
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Which electrical circuit will have no current?
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What is the word used to describe how fast electrical energy is used?
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A resistor in a circuit becomes very hot and starts to burn. This is because the resistor is dissipating too much:
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High power resistors are usually large with heavy leads. The size aids the operation of the resistor by:
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What is the output voltage of an amplifier with a gain of 20 dB and an input voltage of 2 V?
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Which type of battery can be repeatedly recharged?
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What voltage does a standard automobile battery usually supply?
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Which component has a positive and a negative side?
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What is a cell that can be repeatedly recharged known as?
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Which of the following is a source of EMF?
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What causes the voltage of a dry cell to drop under high current demand?
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To increase the current capacity of a battery, how should several cells be connected?
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What is the most common function of a diode?
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Which type of modulation is most commonly used for VHF and UHF voice repeaters?
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Which of the following is a form of amplitude modulation?
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What is the primary advantage of single sideband over FM for voice transmissions?
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Which of the following measurements are commonly made using a multimeter?
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In circuit theory, what theorem states that any linear circuit can be represented as an equivalent source with parallel equivalent resistance?
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Which of the following is a safety hazard of a 12-volt storage battery?
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What is connected to the green wire in a three-wire electrical AC plug?
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Which materials are commonly considered good electrical insulators?
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What causes resistors to sometimes heat up when they are in use?
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Which of these materials is the best conductor of electricity?
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What term is used to describe a material that readily allows electrical current to flow?
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If a length of metal in a circuit is conducting electricity very well, what is the best description of its resistance?
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What does the letter 'R' symbolize in electrical terminology?
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What is the reciprocal of resistance called?
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When working on 'transformerless' power supplies, which safety concern is most critical?
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What is the safest way to prevent unauthorized persons from using your amateur station at home?
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How can you best keep unauthorized persons from using a mobile amateur station in your car?
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What is a primary reason for using a key-operated on/off switch in your station's main power line?
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At what electrical current level can it be fatal to humans?
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Which organ can be severely impacted by exposure to a low amount of electrical current?
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What is considered the minimum voltage that can be dangerous to humans?
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If you find someone being burned by high voltage, what should your first action be?
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What is the safest method to remove an unconscious individual from contact with a high voltage source?
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Study Notes
Electrical Energy
- The higher the wattage of a light bulb, the faster it will use electrical energy.
- The 150 watt light bulb will use electrical energy the fastest.
- The basic unit of electrical power is the watt.
- Power is expressed in watts.
- Voltage and current should be multiplied together to find power.
- Volts and amperes multiplied together give the unit "watts".
- A resistor that is dissipating too much power will become hot and may start to burn.
- High power resistors are usually large with heavy leads to allow heat to dissipate more readily.
- A resistor marked 20 watts will be able to dissipate the most heat.
AC & DC Power
- 120 Vdc has higher energy compared to 120 Vrms.
Safety
- It is dangerous to work on a power supply while it is operating because of the risk of electric shock.
- A key-operated on/off switch in the main power line can be used to keep unauthorized people from using your amateur station.
- As little as 1/10 of an ampere of electrical current flowing through the human body can be fatal
- The heart can be fatally affected by a very small amount of electrical current
- The minimum voltage that is usually dangerous to humans is 30 volts
- To safely remove an unconscious person from contact with a live high voltage source, turn off the high voltage switch first.
- Before checking a fault in a mains operated power supply, it is safest to turn off the power and remove the power plug.
- The safety hazard of a 12-volt storage battery is that shorting the terminals can cause, burns, fire, or an explosion, touching the terminals with the hands can cause electrical shock, and RF emissions from the battery.
- The green wire in a three-wire electrical AC plug connects to the safety ground.
Electronics
- The gain of an amplifier is the ratio of the output voltage to the input voltage
- The output voltage of an amplifier with a gain of 20dB and an input voltage of 2V is 10V.
- An important difference between a conventional flashlight battery and a lead-acid battery is that only the lead-acid battery can be repeatedly recharged.
- A standard automobile battery usually supplies about 12 volts.
- A battery has a positive and a negative side.
- A battery that can be repeatedly recharged by supplying it with electrical energy is known as a storage cell.
- A lead acid battery is a source of EMF.
- The voltage of a dry cell may drop when supplying a great deal of current due to the cell's internal resistance.
- The carbon-zinc or flashlight cell is the most common primary cell in use today, and cannot be recharged.
- Nickel-cadmium batteries should not be discharged to less than 1.0 volt per cell.
- To increase the current capacity of a cell, several cells are connected in parallel
- To increase the voltage output of a battery, several cells are connected in series.
- Nickel-cadmium batteries should never be short-circuited.
- Good electrical insulators include glass, air, plastic and porcelain.
- Resistors sometimes get hot when in use because some electrical energy passing through them is lost as heat.
- Copper is the best conductor of electricity out of the listed materials.
- The material that will most readily allow an electric current to flow is called a conductor.
- A length of metal that conducts electricity very well will have a low resistance
- The symbol "R" is the symbol for resistance.
- The reciprocal of resistance is conductance.
- Voltage drop is the voltage developed across the terminals of a component.
- The resistance of a conductor changes with temperature.
- Carbon is the most common material used to make a resistor
- One should be very careful when working on "transformerless" power supplies because one side of the line cord is connected to the chassis.
- The most common function of a diode is as a rectifier.
- Thermistors, RTDs and thermocouples are all thermal sensing elements.
Radio & Modulation
- The most commonly used modulation for VHF and UHF voice repeaters is FM.
- Amplitude modulation takes many forms, including single sideband, spread-spectrum, packet radio, and phase shift keying.
- The most commonly used modulation for VHF packet radio transmissions is spread spectrum.
- Single sideband (SSB) is most often used for long-distance or weak signal contacts on the VHF and UHF bands.
- The primary advantage of single sideband (SSB) over FM for voice transmissions is that SSB signals have a narrower bandwidth, are easier to tune and are less susceptible to interference.
Math
- The graph of y = logb x is assymptotic to x = 0.
Other
- A multimeter is commonly used to measure voltage and resistance.
- Norton's theorem states that any linear circuit can be represented as an equivalent source with parallel equivalent resistance.
- The ECT examination is equivalent to a civil service licensure examination by RA 8010.
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Description
This quiz covers essential concepts related to electrical energy, wattage, and safety practices while working with electrical systems. You will learn about the relationship between voltage, current, and power, as well as important safety precautions to avoid electric shock. Test your knowledge on both alternating and direct current power.
