Direct Current and Cell Types Quiz

Questions and Answers

What is the unit of frequency?

Hertz (Hz) (correct)

Henry (H)

Joule (J)

Ohm (Ω)

What does the relationship $t = 1/f$ express?

The relationship between current and resistance.

The relationship between periodic time and frequency. (correct)

The relationship between energy and power.

The relationship between voltage and current.

Which type of current flows in one direction only?

Pulsating current

Alternating current (AC)

Direct current (DC) (correct)

Reactive current

What is the process called when an inductor induces a current in another nearby inductor?

Mutual inductance Signup and view all the answers

What does Lenz's law state regarding induced current?

It opposes the change in flux that produces it. Signup and view all the answers

What is the unit of inductance?

Henry (H) Signup and view all the answers

Which factors determine the electrical characteristics of an inductor?

Material of the core and physical dimensions Signup and view all the answers

What does Faraday's law indicate about induced electromotive force (emf)?

It depends on the relative velocity of the conductor cutting magnetic lines. Signup and view all the answers

What is the primary function of static dischargers or static wicks on an aircraft?

To dissipate static charge into the atmosphere Signup and view all the answers

Which materials are considered good conductors due to their high number of free electrons?

Aluminium and copper Signup and view all the answers

What typically protects static-sensitive devices from stray static charges?

Using wrist straps and grounding leads Signup and view all the answers

What happens to an atom when electrons are transferred between two materials?

The atom acquires a net positive or negative charge Signup and view all the answers

In a stable atom, how do the numbers of protons and electrons relate?

The number of protons and electrons is equal, making the atom neutral Signup and view all the answers

What unit is commonly used to measure electrostatic charge for practical purposes?

Coulomb Signup and view all the answers

What is a free electron in a conductive material?

An electron that can move freely within the material Signup and view all the answers

What characteristic of materials makes them suitable as insulators?

Low number of free electrons Signup and view all the answers

What factors influence the magnitude of the induced e.m.f. in a conductor?

Strength of the magnetic field Signup and view all the answers

What is the relationship between power and energy in an electrical system?

Power is the rate at which energy is converted. Signup and view all the answers

What occurs when a conductor cuts through a magnetic field at right angles?

An e.m.f. is induced. Signup and view all the answers

Which of the following best describes ferromagnetic materials?

They demonstrate strong magnetic properties like iron. Signup and view all the answers

In electromagnetic induction, what is required to generate electricity?

Movement in conjunction with a magnetic field and a closed conductor. Signup and view all the answers

What does the unit of energy, the joule (J), represent?

The capacity to do work Signup and view all the answers

When the angle between a conductor and magnetic field lines is 90°, what effect does it have on induced e.m.f.?

It maximizes the induced e.m.f. Signup and view all the answers

How is the magnetic field of a conductor described?

It spreads out around the conductor in concentric circles. Signup and view all the answers

What is the main difference between primary cells and secondary cells?

Primary cells produce electricity from chemicals used up, while secondary cells convert energy back into chemicals. Signup and view all the answers

What is essential to observe when removing and replacing aircraft batteries?

The manufacturer's guidelines for correct isolation must be followed. Signup and view all the answers

How can the strength of an electric field be defined?

Proportional to the applied potential difference and inversely proportional to distance. Signup and view all the answers

What characterizes the interaction between charged bodies with the same polarity?

They repel each other. Signup and view all the answers

What causes static electricity in insulators?

The separation of electrons and protons due to rubbing two materials. Signup and view all the answers

What phenomenon is indicated by the electric field created between charged parallel metal plates?

Capacitance storage. Signup and view all the answers

What happens to static charges over time in insulating materials?

They eventually dissipate due to dielectric losses. Signup and view all the answers

What is the primary aim of managing static electricity on an aircraft?

To equalize the potential of all points on the aircraft's surfaces. Signup and view all the answers

What happens to an atom when it loses electrons?

It becomes a positive ion. Signup and view all the answers

According to Kirchhoff's voltage law, what is the relationship of potential drops in a closed network?

The sum is equal to zero. Signup and view all the answers

What does Ohm's law state about the relationship between current and voltage in a conductor?

Current is directly proportional to voltage. Signup and view all the answers

In the formula $I = \frac{Q}{t}$, what does 'I' represent?

Current. Signup and view all the answers

What is the unit of resistance?

Ohm. Signup and view all the answers

What does the electromotive force (e.m.f.) create in a circuit?

Current flow. Signup and view all the answers

If a steady current of 3A flows for two minutes, how much charge is transferred?

180 Coulombs. Signup and view all the answers

Which statement describes the relationship between voltage and charge according to the formula $V = \frac{W}{Q}$?

Voltage is the energy required to move charge. Signup and view all the answers

Study Notes

Frequency and Periodic Time

Frequency measures how many cycles of a waveform occur in one second, expressed in hertz (Hz).
Periodic time (or period) is the duration of one complete cycle of the waveform.
Relationship: t = 1/f or f = 1/t.

Alternating Current vs. Direct Current

Direct current (DC) flows in one direction only, whereas alternating current (AC) reverses direction periodically.
Waveforms graphically represent voltage or current variations in AC circuits.

Inductors

Inductors store electrical energy in a magnetic field, utilized in chokes, filters, and selective circuits.
The electrical properties of inductors depend on core material, coil turns, and physical dimensions.

Self-Inductance and Mutual Inductance

Mutual inductance occurs when a changing current in one inductor induces a current in another close inductor.
Self-inductance (L) refers to a back electromotive force generated by changes in current, measured in henries (H).

Faraday's and Lenz's Laws

Faraday's law states that the induced electromotive force (emf) depends on how quickly the conductor cuts magnetic flux lines.
Lenz's law indicates that the induced current opposes the change in magnetic flux that produces it.

Electromagnetic Induction

The generated electromotive force (emf) relates to the conductor's length, magnetic field strength, and relative velocity.
Electricity generation requires movement of a closed conductor within a magnetic field.

Electromagnetism and Inductors

A magnetic field is the area around a magnet where magnetic forces are exerted; it surrounds a conductor carrying an electric current.
Ferromagnetic materials (like iron, nickel, and cobalt) have strong magnetic properties and react significantly to external magnetic fields.

Power and Energy

Power (P), measured in watts (W), is the rate of energy conversion, defined as P = W/t.
Energy is the capacity to do work, measured in joules (J). It can be transformed between forms.
Primary cells are non-rechargeable, while secondary cells can be recharged through reversible chemical reactions.

Direct Current Safety

Follow Aircraft Maintenance Manual (AMM) guidelines for isolating batteries before removal or replacement in aircraft.

Electric Field

An electric field is the force region around a charged particle, defining the direction and magnitude of the force on other charges.
Between two parallel plates, the electric field strength (E) depends on applied potential difference and plate distance.

Electrostatics and Capacitors

Like charges repel, while opposite charges attract; static electricity can build from friction and may need to be dissipated in aircraft.
Stray static charges can damage sensitive devices; proper ESD precautions include wrist straps and grounded packaging.

Electron Theory

Charge value is expressed in coulombs. Conductors (e.g., copper, aluminum) have many free electrons that allow current flow.
Electrons can be detached from atoms, creating positive or negative ions, which result in electrostatic effects.

Kirchhoff's Laws

Kirchhoff's Current Law: Total current at a junction is zero.
Kirchhoff's Voltage Law: The sum of potential drops in a closed circuit is zero.

Ohm's Law

Current (I) is directly proportional to voltage (e.m.f.) and inversely proportional to resistance (R).
The basic circuit includes a voltage source (battery) and a load (resistor).

Current, Voltage, and Resistance

Current (I), measured in amperes (A), is the flow rate of charge (1 A = 1 coulomb/second).
Voltage (V) is the electromotive force that drives current flow, defined as the energy per charge (1 V = 1 J/C).
Resistance (R), measured in ohms (Ω), is the opposition to charge flow caused by collisions within the material.

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Description

Test your knowledge on primary and secondary cells in direct current systems. This quiz will explore the chemical processes involved in energy conversion, including the differences between non-rechargeable and rechargeable cells. Understand the principles behind electrical energy generation and storage.