Electricity Review

Topics covered

• Characteristics of Dynamic Electricity– Intensity– Resistance– Potential Difference– Energy– Electrical Power– Work

• Circuit designs

Characteristics

1. IntensityA. Definition

• The number of charges that flow past a given point in 1 second

Characteristics

B. Units:– The Current Intensity is measured in Amperes (A)

C. Formula:– I = q/∆t

• Where I = Intensity (A)

q = Charges (C)

∆t = variation in time (sec)

D. In a circuit:

A

Characteristics

2. ResistanceA. Definition

• The ability to slow down the electrons. The ability of a material to hinder the flow of the electric curent.

Characteristics

B. Units:– The Resistance is measured in Ohms (Ω)

C. Formula:– V = R I

• Where V = Potential Difference (V)R = Resistance (Ω) I = Intensity (A)

D. In a circuit:

Characteristics

E. Factors affecting resistance– Nature of the substance

• Better Conductor = Less resistance

– Length• The shorter, the less resistance

– Diameter• The fatter, the less resistance

– Temperature• The colder, the less resistance

Characteristics

3. Potential DifferenceA. Definition

• The amount of energy transferred between two points in an electrical circuit.

V

Characteristics

B. Units:– The Potential Difference is measured in Volts (V)

C. Formula:– V = E/q

• Where V = Potential Difference (V)

E = Electric Energy (J)

q = Charge (C)

D. In a circuit:

V

Characteristics

4. Electrical PowerA. Definition

• The amount of work an electrical device can perform per second or how much energy it can transform in a period of time.

Characteristics

B. Units:– The Electrical Power is measured in Watts (W)

C. Formula:– Pe = W/∆t

• Where Pe = Electrical Power (W) W = Work (J) ∆t = Time Interval (sec)

– Pe = V I• Where Pe = Electrical Power (W)

V = Potential Difference (V) I = Intensity (A)

Characteristics

C. Formula (Continued)– E = Pe∆t

• Where E = Electrical Energy (J or kWh)

Pe = Electrical Power (Pe)

∆t = Time Interval (sec or hours)

Electrical Circuits

Electrical Circuits

• Types of electrical circuitsA. Series circuit

• Definition:– Circuit that contains only one branch or path for the

electrons to follow.

• Characteristics– If one element is defective, the electricity does not flow– The intensity is the same all around the circuit– The resistance adds up

Electrical Circuits

B. Parallel circuit• Definition

– Circuit that contains at least one branch or paths for the electrons to follow.

• Characteristics– If an element is defective, the elements on that

particular branch will stop working only– Resistance is shared (so resistance is lower)– Current intensity adds up

Electrical oddities

• A switch must be closed in order to allow the energy to flow

• A light will only light up when the electrons complete a full circuit (one side of the power source to another)