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Question:

Which of the following statements is correct regarding inductors?

A An inductor blocks AC but allows DC to pass.

explanation

An inductor resists a change in current that is why it blocks AC. The equation of an inductor is \(\frac{\mathrm{di} }{\mathrm{dt} } = \frac{\mathrm{V} }{\mathrm{L} }\) . If you apply DC across an inductor, it will stabilize to some current flow based on the maximum current available from the current/voltage source. In this mode, the inductor presents very low resistance, so it can be said that it allows DC to pass.

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In a transformer ____

All of the above

A transformer uses the properties of an inductor to transform the level of voltage in a circuit. AC flowing in wires wrapped around an iron core magnetizes the core, and in turn produces a changing magnetic field on the core. This changing magnetic field generates a voltage in a neighbouring coil of wire. Depending on the number of turns on the wire in the primary versus the secondary coil, a smaller or larger voltage can be induced in the secondary coil.

What is the voltage across and current through the resistor R when the switch is open?

0 A Current; 0 V voltage

When the switch is open, there is no voltage or current.

What is the primary difference between a rectifier and an inverter?

a rectifier converts an AC input to DC while an inverter converts a DC input to AC

A diode allows current to pass easily in one direction and blocks current in the other direction. Diodes are commonly used for rectification which is the conversion of alternating current (AC) into direct current (DC). Because a diode only allows current flow in one direction, it will pass either the upper or lower half of AC waves (half-wave rectification) creating pulsating DC. Multiple diodes can be connected together to utilize both halves of the AC signal in full-wave rectification.

What should the temperature of a typical soldering iron be when joining two wires together?

500 to 600 degrees Fahrenheit

To properly melt solder, you should use a soldering iron heated between 500 and 600 degrees Fahrenheit .

What would happen to the voltage if the current doubles and the resistance increases four times?

The voltage will increase 8 times.

Ohm's Law states that V=IR. If current doubles and the resistance increases four times then V = 2I * 4R = 8IR i.e. the voltage increases 8 times.

Two 16 ohm speakers are connected in parallel to an amplifier that provides a 32 volt output. The voltage across each speaker is?

32 volts

The voltage across parallel resistors is the same.

Current I is passing through a load of resistance R. If the voltage across the load doubles and the resistance of the load is reduced by half then what is the amount of current passing through the load?

4I

According to Ohm's law, the relationship between voltage, current and resistance is V = IR which can be rearranged as \(I = \frac{\mathrm{V} }{\mathrm{R} } \). If the voltage doubles and the resistance is reduced by half then \(I_1 = \frac{\mathrm{2V} }{\mathrm{0.5 \Omega } } = 4 \frac{\mathrm{V} }{\mathrm{R} } = 4I\) . Therefore, the current flowing through the load will increase four times.

The two most commonly used metals in solder are

tin and lead

Typical solders are almost equal parts tin and lead.

Electrical power can be calculated with the following formula P = (I × V). What does the letter I represent in this formula?

current

The letter P represents power, which is measured in watts. The letter I represents current, which is measured in amperes. The letter V represents voltage which is measured in volts.

Which function does the receiving antenna provide in radio communication?

It catches the signal out of the air.

The broadcast antenna is used to broadcast the signal over the air. The mixer combines the signal and carrier wave. The de-mixer separates the carrier and the signal.

Which of the following is not an application of a transistor?

Transformer

A transistor is a semi-conductor device designed to amplify and switch electronic signals and electric power. A transistor has a wide range of applications including electric switch, amplifier, voltage and current regulator etc. A transistor is different from a transformer, a transistor is a semi-conductor device while a transformer is an electromagnetic device.

An ammeter measures what?

Current

An ammeter measures current.

The current in the 4 ohm resistor is

1 amp

Use Ohm's law : V=IR. The total resistance in the circuit is 10 ohms (add the resistance for serial resistors). Therefore the total current across either of the resistors is \(I = \frac{\mathrm{V} }{\mathrm{R} } = \frac{\mathrm{10} }{\mathrm{10} } = 1\) amp.

Which of the following is NOT a type of resistor?

dielectric

A potentiometer is a three terminal resistor with a sliding contact. A rheostat is a two terminal variable resistor. A variable resistor is any resistor that allows you to change the amount of resistance. Potentiometers and rheostats are both types of variable resistors.