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**BASIC ELECTRICITY OBJ **

**01-10: DACBDAAADA**

**11-20: BCBBBCBAAB**

**21-30: ACBBCBABDC**

**31-40: DBDDCACAAB**

**COMPLETED**

*===================================*

**ANSWER FIVE(5) QUESTIONS ONLY**

**(1a)**

**The purpose of colouring carbon resistors is to indicate their resistance value through a colour code system.**

**(1b)**

**(i) Brown Yellow Red and Gold**

**Brown = 1, Yellow = 4, Red = Multiplier (10²), Gold = ±5%**

**Resistance value = 14 x 10² **

**= 1400Ω **

**Maximum value = 1400 x 1.05 **

**= 1470Ω **

**Minimum value: 1400 x 0.95 **

**= 1330Ω**

**(ii) Red Black Green and Silver**

**Red = 2, Black = 0, Green = Multiplier (10⁵), Silver = ±10%**

**Resistance value = 20 x 10⁵**

**= 2,000,000Ω **

**= 2 MΩ **

**Maximum value = 2,000,000 x 1.10 **

**= 2,200,000Ω **

**Minimum value = 2,000,000 x 0.90 **

**= 1,800,000Ω**

**(iii) Orange Brown Blue and Gold**

**Orange = 3, Brown = 1, Blue = Multiplier (10⁶), Gold = ±5%**

**Resistance value = 31 x 10⁶ **

**= 31,000,000Ω **

**= 31 MΩ **

**Maximum value = 31,000,000 x 1.05 **

**= 32,550,000Ω **

**Minimum value = 31,000,000 x 0.95 **

**= 29,450,000Ω**

**(iv) Blue Black Black and Silver**

**Blue = 6, Black = 0, Black = Multiplier (10⁰), Silver = ±10%**

**Resistance value = 60 x 10⁰**

**= 60Ω **

**Maximum value = 60 x 1.10 **

**= 66Ω **

**Minimum value = 60 x 0.90 **

**= 54Ω**

**(v) Brown Blue Red and Gold**

**Brown = 1, Blue = 6, Red = Multiplier (10²), Gold = ±5%**

**Resistance value = 16 x 10² **

**= 1600Ω **

**Maximum value = 1600 x 1.05 **

**= 1680Ω **

**Minimum value = 1600 x 0.95 **

**= 1520Ω**

*===================================*

**(2a)**

**(i) Electromotive force (EMF): Electromotive force, denoted as EMF represents the electrical energy per unit charge that a source of electrical energy can provide. It is measured in volts (V).**

**(ii) Potential difference: Potential difference is the difference in electric potential between two points in an electric circuit, representing the work done per unit charge in moving a charge between those two points. It is measured in volts (V).**

**(iii) Current: Current is the flow of electric charge through a conducting medium, measured as the rate of flow of charge through a given cross-sectional area. It is measured in amperes (A).**

**(2b)**

**Given:**

**Voltage (V) = 240V**

**Current (I) = 2.4A**

**Total Resistance (RT) = V/I**

**RT = 240/2.4**

**RT = 100Ω **

**Total Resistance (RT):**

**= Sum of parallel resistance (RP) + Sum of series resistance (RS)**

**RP = RT – RS**

**RS = 70Ω**

**RP = 100 – 70**

**RP = 30Ω **

**1/RP = 1/90 + 1/B**

**1/30 = 1/90 + 1/B**

**1/B = 1/30 – 1/90**

**1/B = (3 -1)/90**

**1/B = 2/90**

**B = 90/2**

**B = 45Ω**

*===================================*

**(3a)**

**(i) Voltage reaches its maximum level **

**(ii) Charging current drops to minimum **

**(iii) Battery temperature stabilizes**

**(3b)**

**Given:**

**Number of identical cells = 9**

**Electromotive force (EMF) = 2v**

**Internal resistance = 0.1Ω **

**Resistance Load = 7.5Ω**

**(i) All In Series:**

**Total EMF = 9 x 2**

**= 18v**

**Total internal resistance = 9 x 0.1**

**= 0.9Ω**

**Total resistance = 0.9 + 7.5**

**= 8.4Ω**

**Current = 18/8.4**

**= 2.14A**

**Potential difference across the load:**

**= 2.14 x 7.5**

**= 16.05Ω**

**(ii) All Cells in Parallel:**

**Total EMF = 2v**

**Total internal resistance = 0.1/9**

**= 0.0111Ω**

**Total resistance = 0.0111 + 7.5**

**= 7.5111Ω**

**Current = 2/7.5111**

**= 0.266A**

**Potential difference across the load:**

**= 0.266 x 7.5**

**= 1.995Ω**

**(iii) 3 Cells in Series and 3 Sets in Parallel:**

**Total EMF in series:**

**= 3 x 2**

**= 6v**

**Total internal resistance in series:**

**= 3 x 0.1**

**= 0.3Ω**

**Total EMF in parallel = 6v**

**Total internal resistance in parallel: **

**= 0.3/3**

**= 0.1Ω**

**Total resistance = 0.1 + 7.5**

**= 7.6Ω**

**Current = 6/7.6**

**= 0.789A**

**Potential difference across the load:**

**= 0.789 x 7.5**

**= 5.92Ω**

*===================================*

**(5a)**

**(i) Inductive reactance is the opposition that an inductor offers to the flow of alternating current. Its unit of measurement is the ohm (Ω).**

**(ii) Capacitive reactance is the opposition that a capacitor offers to the flow of alternating current. Its unit of measurement is the ohm (Ω).**

**(iii) Impedance is the total opposition that a circuit offers to the flow of alternating current. It is a combination of resistance, inductive reactance, and capacitive reactance, measured in ohms (Ω).**

**(5b)**

**Given:**

**Voltage (V) = 100 V**

**Frequency (f) = 50 Hz**

**Resistor (R) = 10 Ω**

**Inductance (L) = 50 mH **

**= 0.05 H**

**Capacitance (C) = 350 μF **

**= 350 × 10⁻⁶F**

**(i) Current (I):**

**Inductive reactance (XL) = 2πFL**

**XL = 2 x π x 50 x 0.05**

**XL = 31.42Ω**

**Capacitive reactance (XC)= 1/(2πFC)**

**XC = 1/(2 x π x 50 x 350 x 10⁻⁶)**

**XC = 91.09Ω**

**Total impedance (Z):**

**1/Z = 1/R + 1/XL + 1/XC**

**1/Z = 1/10 + 1/31.42 + 1/91.09**

**1/Z = 0.1+ 0.0318 + 0.01098**

**1/Z = 0.14278**

**Z = 1/0.14278**

**Z = 7.0Ω**

**Current (I) = V/Z **

**I = 100/7.0**

**I = 14.29A**

**(ii) Power Factor:**

**PF = R/Z**

**PF = 10/7.0**

**PF = 1.43**

**(iii) Angle of Lag (θ):**

**θ = Cos⁻¹(PF)**

**θ = Cos⁻¹(1)**

**θ = 0°**

**(iv) Power Consumed by the Circuit:**

**P = VI Cosθ **

**P = 100 x 14.29 Cos(0)**

**P = 100 x 14.29 x 1**

**P = 1429W**

*===================================*

**(6a)**

**(i) Accuracy**

**(ii) Resolution**

**(iii) Response time**

**(6b)**

**(i) 0 – 5 mA:**

**R = (50×10⁻³x50)/ (5×10⁻³) **

**R = 500Ω**

**(ii) 0 – 10 A:**

**R = (50×10⁻³x50)/ 10 **

**R = 0.25Ω**

**(iii) 0 – 15 A:**

**R = (50×10⁻³x50)/ 15 **

**R = 0.167Ω**

**(iv) 0 – 50 V:**

**R = 50/(50×10⁻³)**

**R = 1kΩ**

**(v) 0 – 100 V:**

**R = 100/ (50×10⁻³) **

**= 2kΩ**

**(vi) 0 – 150 V:**

**R = 150/ (50×10⁻³) **

**R = 3kΩ**

*===================================*

**(7a)**

**(i) Heating Effect: When an electric current flows through a conductor, it produces heat due to the resistance of the material. This is commonly used in devices such as electric stoves and toasters to generate heat.**

**(ii) Magnetic Effect: An electric current flowing through a conductor creates a magnetic field around it. This principle is the basis for electromagnets used in various applications such as electric motors and transformers.**

**(iii) Chemical Effect: Electric currents can cause chemical reactions in certain materials. This effect is utilized in processes like electroplating and electrolysis, where a chemical change is induced by passing an electric current through a solution.**

**(7b)**

**Given:**

**Resistance (R) = 30Ω**

**Voltage (V) = 240V**

**Time (t) = 1 hour = 3600 seconds**

**Power (P) = V²/R**

**P = (240)²/30**

**P = 1920W**

**Energy consumed (E):**

**E = Power x Time**

**E = 1920 x 3600 **

**E = 6,912,000J**

**E = 6,912,000/3,600,000 **

**E = 1.92kWh**

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