Circuit analysis/ Chapter 1

What is electrical engineering?

The branch of engineering that studies and designs systems that generate, control, transmit, and use electrical energy and signals.

What is an electric circuit?

A closed path that allows electric current to flow.

What is electricity?

The movement or interaction of electric charges.

What is electric charge?

A fundamental property of matter that can be positive or negative and is measured in coulombs (C).

What are the two types of electric charge?

Positive and negative.

What happens when like charges interact?

They repel each other.

What happens when opposite charges interact?

They attract each other.

What is the SI unit of electric charge?

The coulomb (C).

What particle carries a positive charge?

The proton.

What particle carries a negative charge?

The electron.

What particle has no electric charge?

The neutron.

Which particles move through a metal conductor?

Electrons.

What is current?

The rate at which electric charge flows through a conductor.

What is the symbol for current?

I

What is the SI unit of current?

The ampere (A).

What does one ampere represent?

One coulomb of charge flowing per second.

What equation defines electric current?

I = Q/t

What does Q represent in I = Q/t?

Electric charge in coulombs.

What does t represent in I = Q/t?

Time in seconds.

What is voltage?

Electrical potential difference between two points.

What is another name for voltage?

Potential difference or electromotive force (EMF).

What is the symbol for voltage?

V

What is the SI unit of voltage?

The volt (V).

What does voltage physically represent?

The amount of energy available to move one coulomb of charge between two points.

What is resistance?

The opposition to the flow of electric current.

What is the symbol for resistance?

R

What is the SI unit of resistance?

The ohm (Ω).

What causes resistance?

The material, length, cross-sectional area, and temperature of the conductor.

What does a resistor do?

It limits current and creates a voltage drop.

What is conductance?

The ease with which current flows.

What is the symbol for conductance?

G

What is the SI unit of conductance?

The siemens (S).

What is the relationship between resistance and conductance?

G = 1/R

What is Ohm's Law?

V = IR

How can Ohm's Law be rearranged to solve for current?

I = V/R

How can Ohm's Law be rearranged to solve for resistance?

R = V/I

What is electric power?

The rate at which electrical energy is transferred or converted.

What is the symbol for power?

P

What is the SI unit of power?

The watt (W).

Power equation using voltage and current

P = VI

Power equation using current and resistance

P = I²R

Power equation using voltage and resistance

P = V²/R

What is electrical energy?

The ability to do work using electrical power over time.

What equation relates energy and power?

W = Pt

What is the SI unit of energy?

The joule (J).

What is a source?

A device that supplies electrical energy to a circuit.

What is a load?

A device that consumes electrical energy.

Give three examples of electrical loads.

Light bulb, resistor, motor.

What is an ideal voltage source?

A source that maintains a constant voltage regardless of the current drawn.

What is an ideal current source?

A source that maintains a constant current regardless of the voltage across it.

What is conventional current?

The assumed flow of positive charge from positive to negative.

How do electrons actually move?

From the negative terminal to the positive terminal.

Why do engineers still use conventional current?

It was established before electrons were discovered and remains the engineering standard.

What is a conductor?

A material that allows electric current to flow easily.

Give three examples of conductors.

Copper, aluminum, silver.

What is an insulator?

A material that strongly resists the flow of electric current.

Give three examples of insulators.

Rubber, glass, plastic.

What is a semiconductor?

A material whose conductivity lies between a conductor and an insulator.

Give two examples of semiconductors.

Silicon and germanium.

What is a closed circuit?

A complete path that allows current to flow.

What is an open circuit?

A broken path where current cannot flow.

What is a short circuit?

A very low resistance path that allows excessive current to flow.

What is Kirchhoff's Current Law (KCL)?

The algebraic sum of currents entering and leaving a node is zero.

Why does KCL work?

Because electric charge cannot accumulate at a node.

What is Kirchhoff's Voltage Law (KVL)?

The algebraic sum of all voltage rises and drops around a closed loop is zero.

Why does KVL work?

Because energy is conserved around a closed loop.

What is a node?

A point where two or more circuit elements are connected by ideal wire.

What is a branch?

A single element connected between two nodes.

What is a loop?

Any closed conducting path in a circuit.

What is a mesh?

A loop that contains no other loops inside it.

What is the reference node?

The node assigned 0 V, called ground.

Why do we assign a reference node?

So every other node voltage can be measured relative to it.

How many node voltages exist in a circuit?

Number of nodes minus one.

When can a node voltage be known immediately?

When an ideal voltage source connects the node directly to ground.

What is nodal analysis?

A circuit-analysis method that uses KCL to solve for unknown node voltages.

What is mesh analysis?

A circuit-analysis method that uses KVL to solve for loop currents.

Why is nodal analysis usually preferred?

Because most circuits have fewer nodes than loops, requiring fewer equations.