Electricity

What are the two fundamental types of charges?

Protons and electrons.

What surrounds electric charges and produces a force?

An electric field.

What is the unit of electric charge?

Coulomb (C).

How many electrons are equivalent to one coulomb of charge?

6.24 × 10¹⁸ electrons.

What is the charge of one electron in coulombs?

-1.602 × 10⁻¹⁹ C.

What is the charge of one proton?

+1.602 × 10⁻¹⁹ C.

What is the formula to find the number of electrons on an object?

Ne = q / qe.

What does each symbol in Ne = q / qe represent?

Ne = number of electrons

What is an electric field?

A region where a charged particle experiences a force.

Do all charged particles produce electric fields?

Yes.

What kind of quantity is an electric field?

A vector quantity (has magnitude and direction).

How is electric field strength defined?

As the force per unit charge: E = F/q.

What is the formula for electric field strength?

E = F / q.

What are the units for electric field strength?

Newtons per coulomb (N/C).

What does the direction of electric field lines indicate?

The direction of the force on a positive charge.

How do electric field lines behave around a negative point charge?

They point inward.

How do electric field lines behave around a positive point charge?

They point outward.

What does the density of electric field lines represent?

The strength of the electric field.

Do electric field lines ever cross?

No.

What does voltage or potential difference represent?

The energy change per unit charge from one point to another.

How is voltage calculated?

V = W / q.

What is the unit of voltage?

Volts (V).

What is current?

The rate of flow of electric charge.

What is the formula for electric current?

I = q / t.

What is the unit of current?

Ampere (A)

What type of current flows in one direction?

Direct current (DC).

What type of current alternates direction?

Alternating current (AC).

What is conventional current?

Flow of positive charge from high to low potential.

What direction do electrons flow in a circuit?

From the negative terminal to the positive terminal.

What is resistance?

The opposition to the flow of electric current.

What is the formula for resistance?

R = V / I.

What are the four factors affecting resistance?

Length

How does length affect resistance?

Longer conductors have higher resistance.

How does cross-sectional area affect resistance?

Smaller area = higher resistance.

How does temperature affect resistance?

Higher temperature = higher resistance.

How does the type of material affect resistance?

More free electrons = lower resistance.

What is Ohm's Law?

V = IR.

What is an ohmic conductor?

A material that obeys Ohm’s law (linear V-I relationship).

Give an example of an ohmic conductor.

Copper or silver wire.

What is a non-ohmic conductor?

A material where resistance changes with conditions (e.g. filament bulbs

What three components are required in a simple circuit?

Power source (DC)

What is a series circuit?

A circuit with only one path for current.

What happens when a component in a series circuit breaks?

The entire circuit stops working.

What is a parallel circuit?

A circuit with multiple paths for current.

What happens when a branch in a parallel circuit breaks?

The rest of the circuit still works.

What is the rule for voltage in series circuits?

Vₜ = V₁ + V₂ + … + Vₙ.

What is the rule for current in series circuits?

Iₜ = I₁ = I₂ = … = Iₙ.

What is the rule for resistance in series circuits?

Rₜ = R₁ + R₂ + … + Rₙ.

What is the rule for voltage in parallel circuits?

Vₜ = V₁ = V₂ = … = Vₙ.

What is the rule for current in parallel circuits?

Iₜ = I₁ + I₂ + … + Iₙ.

How do you calculate total resistance in a parallel circuit?

Use Ohm's law: V = IR.

How is an ammeter connected in a circuit?

In series with the component.

What does an ammeter measure?

Electric current.

How is a voltmeter connected in a circuit?

In parallel with the component.

What does a voltmeter measure?

Voltage across a component.

Why must a voltmeter have high resistance?

To prevent current from being diverted through it.

What is power in an electric circuit?

The rate of energy transformation.

What is the formula for power?

P = VI.

What are the units of power?

Watts (W).

What is the formula for energy in circuits?

W = VIt.

Which resistor in a series circuit dissipates more energy?

The one with higher resistance.

What is the formula for power in terms of current and resistance?

P = I²R.

Which resistor in a parallel circuit dissipates more energy?

The one with lower resistance.