Electronics Flashcards

What is the frequency of Direct Current (DC)?

Answer: 0 Hz

Direct Current (DC) is an electric current that flows in only one direction, maintaining a constant polarity. Unlike Alternating Current (AC), DC does not periodically reverse its direction or magnitude in a cyclical pattern. Therefore, it has no cycles per second, meaning its frequency is 0 Hz.

What does the following image represent?

Answer: Ground

The image (three horizontal lines decreasing in length, often connected to a circuit) is the standard electrical symbol for 'Ground'. This symbol represents a common reference point in an electrical circuit, typically considered to be at zero potential, and often connected to the earth or a chassis for safety and stability.

An ideal fuse should have a:

Answer: Low melting point and a high current rating.

An ideal fuse is designed to protect a circuit by melting and breaking the connection when current exceeds a safe limit. It must have a low melting point to react quickly to overcurrent conditions. While the term 'high current rating' can be ambiguous, in this context, it implies the fuse material can efficiently carry its rated current without degradation, yet still blow quickly due to its low melting point when that rating is exceeded.

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?

Answer: 100 ohms

Ohm's Law states that V = I * R, where V is voltage, I is current, and R is resistance. To find the maximum resistance for which current flows without blowing the fuse, we use the fuse's maximum current rating. Rearranging Ohm's Law, R = V / I. Plugging in the values, R = 80 V / 0.8 A = 100 ohms. If the resistance were lower than 100 ohms, the current would exceed 0.8 A, causing the fuse to blow.

A capacitor stores energy in the form of:

Answer: Electric Field

A capacitor consists of two conductive plates separated by a dielectric (insulating) material. When a voltage is applied across the plates, electric charge accumulates on them, creating an electric field in the dielectric material between the plates. The energy stored in a capacitor is held within this electric field.

What is the basic operation of a step-up transformer?

Answer: Both options 1 and 2

An ideal transformer conserves power between its primary and secondary coils (P_primary = P_secondary). A step-up transformer is designed to increase (step up) the voltage from the primary to the secondary side. To maintain power conservation (P = V * I), if the voltage is stepped up, the current must proportionally decrease (step down) in the secondary coil.

The generated force on a current carrying wire can be increased by

Answer: Increasing the amount of current flowing.

The force (F) on a current-carrying wire in a magnetic field is directly proportional to the current (I) flowing through the wire, the strength of the magnetic field (B), and the length of the wire (L) within the field (F = BILsinθ). Therefore, increasing the amount of current flowing will directly increase the generated force.

A capacitor is also known as:

Answer: Condenser

The term 'condenser' is an older, but still occasionally used, name for a capacitor. Both terms refer to an electrical component designed to store electrical energy in an electric field. While 'capacitor' is the more modern and widely accepted term in electronics, 'condenser' is still recognized, particularly in certain contexts like automotive ignition systems.

Four capacitors are connected in parallel, each having a capacitance of 4 farads. What will be the equivalent capacitance of these capacitors?

Answer: 16 F

When capacitors are connected in parallel, their equivalent capacitance is simply the sum of their individual capacitances. For four capacitors, each with a capacitance of 4 Farads, connected in parallel, the total equivalent capacitance is 4 F + 4 F + 4 F + 4 F. This sums up to 16 Farads.

The electrical symbol in the figure represents which of the following?

Answer: Galvanometer

The electrical symbol in the figure (a circle with a 'G' inside) is the standard representation for a galvanometer. A galvanometer is an electromechanical instrument used to detect and indicate the presence, direction, or magnitude of an electric current, typically by means of a moving coil in a magnetic field.

An inductor stores energy in the form of

Answer: Magnetic field

An inductor is a passive electrical component, typically a coil of wire, that stores energy in a magnetic field when electric current flows through it. When the current changes, the magnetic field also changes, inducing a voltage that opposes the change in current, according to Faraday's law of induction.

What does the following image represent?

Answer: Diode

The image (a triangle pointing to a line, with two terminals) is the standard electrical symbol for a 'Diode'. A diode is a semiconductor device that allows current to flow primarily in one direction (forward bias) while blocking it in the opposite direction (reverse bias), acting like a one-way valve for electricity.

Which of the following statements is incorrect regarding a transformer?

Answer: Secondary current of a step-down transformer is less than its primary current.

For an ideal transformer, power is conserved (P_primary = P_secondary). Since power (P) equals voltage (V) multiplied by current (I), a step-down transformer decreases the voltage from the primary to the secondary side. To keep the power constant, the secondary current must increase proportionally. Therefore, the statement that the secondary current of a step-down transformer is less than its primary current is incorrect; it should be greater.

Which of the following statements is incorrect regarding Ohm's Law?\t

Answer: Voltage is inversely proportional to the resistance.

Ohm's Law is expressed as V = I * R. This equation shows that voltage (V) is directly proportional to current (I) when resistance (R) is constant. It also shows that voltage (V) is directly proportional to resistance (R) when current (I) is constant. Therefore, the statement 'Voltage is inversely proportional to the resistance' is incorrect; voltage is directly proportional to resistance.

If three different resistors are connected in parallel and a voltage is applied across them, which of the following statements is correct?

Answer: The greatest resistance has the least power loss across three resistances.

When resistors are connected in parallel, the voltage (V) across each resistor is the same. The power loss (P) in a resistor can be calculated using the formula P = V^2 / R. Since V is constant for all parallel resistors, power loss is inversely proportional to resistance (P ∝ 1/R). This means that a higher resistance will dissipate less power, so the greatest resistance will have the least power loss.

A microwave is consuming 800 W power using a standard North American 120 V power supply. What is the approximate amount of current flowing?\t

Answer: 7 amperes

To calculate the current flowing, we use the power formula P = V * I, where P is power, V is voltage, and I is current. Rearranging the formula to solve for current, I = P / V. Plugging in the given values, I = 800 W / 120 V. This calculation yields approximately 6.67 amperes, which rounds to 7 amperes.

Which of the following is a unit of power?\t

Answer: All of the above

Power is defined as the rate at which energy is transferred or work is done. The standard SI unit for power is the Watt (W). By definition, one Watt is equivalent to one Joule per second (J/s). Additionally, from the formula P = V * I (Voltage x Current), power can also be expressed in Volt-Amperes (V.A). Therefore, all listed options are valid units of power.

Which of the following is true regarding an AC signal?\t

Answer: The smaller the time period, the greater the frequency.

For any periodic signal, including an AC signal, frequency (f) and time period (T) are inversely related by the formula f = 1/T. This means that if the time period (the duration of one complete cycle) is smaller, the frequency (the number of cycles per second) will be greater. Conversely, a longer time period corresponds to a lower frequency.