ASVAB Electronics Practice Test 2
Which of the following is a unit of power?
Power is the rate of doing work i.e. Power = Work/time = J/s. Electrical power is described as P=VI and the unit of power is Watt (W). Power is the product of current and voltage, so it can also be written as V.A where V represents the voltage and A represents the current.
The electrical symbol in the figure represents which of the following?
The given electrical symbol represents a galvanometer. A galvanometer is a type of sensitive ammeter. It is an instrument for detecting electric current.
Four capacitors are connected in parallel, each having a capacitance of 4 farads. What will be the equivalent capacitance of these capacitors?
Capacitors are added in parallel. In the given question, four capacitors (each having 4 F capacitance) are connected in parallel then their equivalent capacitance would be 4+4+4+4=16 F.
What does the following image represent?
The given image represents a diode. A diode is a two terminal electrical equipment which conducts electrical current in one direction only.
A fuse rated at 0.8 A blows when the switch is closed. If an 80 V supply is supplying power to the circuit, what would be the maximum possible value of the resistance for which the current flows through the circuit?
An ideal fuse should have a:
The ideal fuse should carry its rated current indefinitely and it should melt quickly on small excess of the current.
A capacitor is also known as:
A capacitor is a passive two-terminal electrical equipment used to store electrical energy electrostatically in an electric field. It is also known as a condenser.
What is the frequency of Direct Current (DC)?
Frequency is the number of occurrences of an event per unit time and can be expressed as Hz. In DC, the charges flow steadily in one direction while charges keep switching directions in AC. Since no switching (events) occur with DC, the frequency is zero.
If three different resistors are connected in parallel and a voltage is applied across them, which of the following statements is correct?
If three different resistances are connected in parallel and a voltage is applied across them then the voltage is same across all the resistances. The formula for finding power is P = VI = V(V/R) = (V^2/R). According to the formula, the resistor with the least value will have the maximum power loss and the resistor with the maximum value will have the least power loss.
What does the following image represent?
The given symbol represents an earth ground which is used for zero potential reference and electric shock protection.
Which of the following is true regarding an AC signal?
Frequency is the number of occurrences of an event per unit time. The relationship between the frequency and time period of an AC signal is f=1/T i.e. frequency is inversely proportional to the time period of an AC signal. The smaller the time period, the greater the frequency of the signal.
A microwave is consuming 800 W power using a standard North American 120 V power supply. What is the approximate amount of current flowing?
The formula for finding electrical power is Power = Voltage x Currerent or P=VI. Rearranged we have I = P/V = 800/120 = 6.67 ? 7 amperes
A capacitor stores energy in the form of:
A capacitor stores electrical energy in the form of electric field because the DC source creates and excess of electrons on the negative plate and a shortage of electrons on the positive plate. The electrostatic attraction between the positive and negative charges keeps the charge intact in the capacitor, even when the voltage source is removed.
What is the basic operation of a step-up transformer?
The basic operation of a transformer is to step up or step down the voltage in the circuit. If the transformer is a step up then it will step up the voltage and step down the current to maintain the power (i.e. P=VI) in primary and secondary sides of the circuit.
Which of the following statements is incorrect regarding a transformer?
A transfomer is a static device so it has no mechanical losses. A transformer only transforms the voltage and the current and the frequency remains same during the transformation process. The power on primary side of an ideal transformer is equal to the power on the secondary side. It the transformer is step-down then the voltage on secondary side must be less than the voltage on its primary side which means that the current on secondary side must be higher than the current on its primary side.
The generated force on a current carrying wire can be increased by
The generated force on a current carrying wire is directly proportional to the amount of current flowing, the length of the wire, and the strength of the magnetic field. Increasing any of these will increase the force on the wire and the capacity to do work.
An inductor stores energy in the form of
When a current is flowing through an inductor, an energy is stored in the form of magnetic field. The formula of energy stored in an inductor is: Energy=(1/2)LI^2.
Which of the following statements is incorrect regarding Ohm's Law?
Ohm's law states that V=IR. According to the law, voltage is directly proportional to both current and resistance while current is inversely proportional to the resistance.