# Lesson Notes By Weeks and Term - Senior Secondary 1

Arrangement of resistors

Term: 2nd Term

Week: 8

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:

Subject:      Physics

Topic:-       Arrangement of resistors

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

1. State and explain the types of arrangement of resistors
2. State and explain the factors affecting electrical resistance

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

 PRESENTATION TEACHER’S ACTIVITY STUDENT’S ACTIVITY STEP 1 INTRODUCTION The teacher reviews the previous lesson on Verification of the ohm’s law Students pay attention STEP 2 EXPLANATION He states and explains the types of arrangement of resistors Students pay attention and participates STEP 3 DEMONSTRATION He states and explains the factors affecting electrical resistance Students pay attention and participate STEP 4 NOTE TAKING The teacher writes a summarized note on the board The students copy the note in their books

NOTE

ARRANGEMENT OF RESISTORS

There are two arrangement of Resistor, which are:

1. Series arrangement
2. Parallel arrangement

SERIES ARRANGEMENT:

When the resistor is connected end to end as shown, they are said to be in series connection

For series connection, each Resistor (R) has different Voltage (V) but the same Current (I) The total Voltage (V) in the Circuit is given as

V= V1+V2+V3……… (x)

From Ohm’s Law V = IR

Which gives,

IR =IR1+IR2+IR3

IR = I (R1+R2+R3)

Therefore the equivalent resistance (R) of the combination is given by

R = R1+R2+R3

PARALLEL ARRANGEMENT

When resistor is arranged side by side such that their corresponding ends join together at two common junctions, the arrangement is known as parallel arrangement.

The combined or equivalent resistance (R) is given by R1

For parallel connection, each Resistor (R) has different current (I) but the same Voltage (V)

The total Current in the Circuit is given as

I = I1+I2+I3…… xx

From Ohm’s Law V = IR

So, I = V

R

Which gives, V =( VV  + V)

R     R1   R2    R3

Therefore the equivalent resistance of the combination is given by

𝑉𝑅 = v(11  +   1)

𝑅1    𝑅2     𝑅3

Therefore the equivalent resistance of the combination is given by

𝟏𝑹 = 𝟏 +     𝟏+     𝟏

𝑹𝟏     𝑹𝟐     𝑹𝟑

Example: Find the equivalent Resistance in the Circuit below

Solution:

Solution:

Two 2Ω Resistors are connected in series with 3Ω and 5Ω resistor.

Calculating the two parallel connected resistors:

R1= 2Ω and R2= 2Ω

1 =    1 +    1

𝑅         2         2

1 =    1

𝑅       1

R = 1Ω

The circuit diagram becomes,

Now calculating the series connection of the resistor:

R = R1+R2+R3

R=3+1+5

R=9Ω

FACTORS AFFECTING ELECTRICAL RESISTANCE

1. Length of conductor
2. Cross-sectional area of conductor
3. Temperature
4. Type or substance of material

EVALUATION:   1. State and explain the two types of resistor arrangement

1. A battery with a terminal voltage of 9 V is connected to a circuit consisting of four 20Ω20Ω and one 10Ω10Ω resistors all in series. Assume the battery has negligible internal resistance
1. Calculate the equivalent resistance of the circuit
2. Calculate the current through each resistor.
3. Calculate the potential drop across each resistor.
4. Determine the total power dissipated by the resistors and the power supplied by the battery.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively