lessons on Electricity, for student's learning.

1. ELECTRICITY

2. PHYSIOLOGICAL EFFECT OF CURRENT
• Electrons can be made to flow across a human body when there is a
potential difference between two points on that person’s body.
• EMS
• Heart is a muscle, it contracts on a regular basis.
• Defibrillator

3. • When the skin is dry resistance of the human body is appx. 1.5 x
10 ³ Ω
• Wet skin 500Ω
• Ohm’s law tells us that current is inversely proportional to resistance.
• I = V/R
• Effects of electric shock may vary on different individuals.
• 1. Resistance depends on geometry of the conductor, infant or child has lower
electrical resistance than an adult.
• 2. resistance depends on whether the whole body is part of the circuit.
• 3. a person is well hydrated or dehydrated.

4. RESISTOR

5. RESISTOR COLOR CODE
•1. The 1st band is the first digit.
•2. The 2nd band is the second digit.
•3. The 3rd band is the number of zeroes.

6. FACTORS AFFECTING RESISTANCE
•1. Length.
•2. Cross-sectional area.
•The resistance R of a wire is directly
proportional to the length of the wire and
inversely to the cross-sectional area. R= ρl/A

7. RESISTOR CONNECTIONS
• Resistor in series.
• 1. Current. The current in each element or resistor is the same
as the current that goes in to the group.ͭ
• 2. Voltage. The sum of individual potential drops is equal to the
potential drop for the whole group.
• 3. Resistance. The sum of the individual resistances is equal to
the resistance of the whole group.

8. PARALLEL CONNECTION
• 1. Current. The current that goes into a junction is equal to the
sum of the branch currents.
• 2. Voltage. The potential drop across the whole combination is
equal to the potential drop across each branch.
• 3. Resistance. The equivalent resistance of the parallel
combination is equal to the reciprocals of the individual
resistances.