⚡ Chapter 11: Electricity

🎯 Class 10 Science Notes (Simple + Exam Focused)

🔌 1. Electric Current

Current (I) = Flow of electric charge
Formula:

I=QtI = \frac{Q}{t}I=tQ​

Where,

• I = Current (Ampere)
  
  

• Q = Charge (Coulomb)
  
  

• t = Time (seconds)
  
  

👉 Hindi: Vidyut dhaara charge ke flow hone ko kehte hain.

🔋 2. Electric Potential and Potential Difference

Electric Potential: Work done to bring a unit charge from infinity to that point.
Potential Difference (V):

V=WQV = \frac{W}{Q}V=QW​

Where,

• W = Work done
  
  

• Q = Charge
  
  

• Unit: Volt (V)
  
  

👉 Hindi: Do binduon ke beech ki energy difference ko potential difference kehte hain.

🧲 3. Ohm’s Law

V=IRV = IRV=IR

Where,

• V = Potential difference
  
  

• I = Current
  
  

• R = Resistance
  Graph: V vs I is a straight line.
  
  

👉 Hindi: Ohm ka niyam kehta hai V current ke proportional hota hai.

🧱 4. Resistance

It is the opposition to the flow of current.
Unit: Ohm (Ω)
Factors affecting resistance:

• Length (R ∝ L)
  
  

• Area (R ∝ 1/A)
  
  

• Material
  
  

• Temperature
  
  

👉 Hindi: Resistance current ke flow mein rukawat hoti hai.

🔄 5. Resistors in Series and Parallel

🔹 Series Combination:

• Total Resistance: R=R1+R2+R3R = R_1 + R_2 + R_3R=R1​+R2​+R3​
  
  

• Current same, Voltage divides.
  
  

🔹 Parallel Combination:

\frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} ]

• Voltage same, Current divides.
  
  

👉 Hindi: Series mein resistance jodte hain, parallel mein ulte jodte hain.

🔥 6. Heating Effect of Electric Current

Formula:

H=I2RtH = I^2 R tH=I2Rt

Used in: Electric heater, bulb, geyser etc.
👉 Hindi: Current se heat generate hoti hai jise hum kaam mein lete hain.

🔌 7. Electric Power

P=VI=I2R=V2RP = VI = I^2R = \frac{V^2}{R}P=VI=I2R=RV2​

• Unit: Watt (W)
  
  

• 1 kW = 1000 W
  
  

• 1 kWh = 1000 watt × 1 hour = 3.6 × 10⁶ joules
  
  

👉 Hindi: Power ka matlab hai kaam karne ki rate.

📘 Important Questions – With Answers

✅ 1 Mark Questions

1. Define 1 volt.
   👉 1 volt is the potential difference when 1 joule of work is done to move 1 coulomb of charge.
   
   

2. What is the SI unit of electric current?
   👉 Ampere (A)
   
   

3. State Ohm’s Law.
   👉 V = IR — Voltage is directly proportional to current if temperature is constant.
   
   

✅ 2 Mark Questions

1. Write two differences between series and parallel circuits.
   
   

Series

Parallel

Current same everywhere

Current divides

Resistance increases

Resistance decreases

2. 
   Calculate current when 5C charge flows in 10 seconds.
   👉
   
   

I=Qt=510=0.5 AI = \frac{Q}{t} = \frac{5}{10} = 0.5\,AI=tQ​=105​=0.5A

✅ 3 Mark Questions

1. Three resistors of 2Ω, 3Ω and 6Ω are connected in parallel. Find total resistance.
   👉
   
   

1R=12+13+16=3+2+16=1⇒R=1 Ω\frac{1}{R} = \frac{1}{2} + \frac{1}{3} + \frac{1}{6} = \frac{3+2+1}{6} = 1 \Rightarrow R = 1\,\OmegaR1​=21​+31​+61​=63+2+1​=1⇒R=1Ω

2. A bulb of 100W works on 220V. Find current and resistance.
   👉
   
   

P=VI⇒I=PV=100220≈0.45 AP = VI \Rightarrow I = \frac{P}{V} = \frac{100}{220} \approx 0.45\,A P=VI⇒I=VP​=220100​≈0.45A R=VI=2200.45≈489 ΩR = \frac{V}{I} = \frac{220}{0.45} \approx 489\,\OmegaR=IV​=0.45220​≈489Ω

✅ 5 Mark Questions

1. Derive expression for heat produced by electric current.
   👉
   
   

W=VIt⇒H=I2RtW = VIt \Rightarrow H = I^2RtW=VIt⇒H=I2Rt

Use Ohm’s law to derive. Explain applications like heaters and bulbs.

2. Explain series and parallel combination with formulas and one example each.
   👉
   Explain resistance formulas, where used (series – decorative lights; parallel – homes).