MCQ Practice — Category 02
Ohm’s Law MCQ
V=IR, Series-Parallel circuits, Kirchhoff’s Law — calculation based sawaal jo interview me aate hain. 5 parts mein divide — apni speed se practice karo.
50 Questions
5 Parts
Easy → Hard
Hinglish Explanation
Select a Part to Practice
Part 01
Basics
Q 1–10
Easy
Start
Part 02
Series-Parallel
Q 11–20
Easy–Med
Start
Part 03
Power Calc
Q 21–30
Medium
Start
Part 04
KVL/KCL
Q 31–40
Med–Hard
Start
Part 05
Gulf Calc
Q 41–50
Hard
Start
Theory + Practical — Ohm’s Law
Ohm’s Law Kya Hai?
Main Mohammad Arif – 12+ saal Gulf aur India ke electrical supervisor. Har electrician ki pehchan Ohm’s Law se hoti hai. Ye electrical engineering ka sabse basic aur important law hai. Gulf interviews mein har practical calculation – chahe cable sizing ho, motor current ho, ya DB load – sab Ohm’s Law ke around ghoomta hai.
Ohm’s Law states: Voltage (V) = Current (I) × Resistance (R). Is formula se hum voltage, current, ya resistance nikaal sakte hain agar do values known hon.
Fig 1 — Ohm’s Law Triangle (V = I × R)
Important: Ohm’s Law sirf linear ohmic conductors ke liye valid hai jahan temperature constant ho. Non-linear devices (diode, transistors) mein ye directly apply nahi hota.
Series Circuit – Formula & Properties
Key Formulas
- R_total = R1 + R2 + R3 + …
- I_total = I1 = I2 = I3 = … (same current)
- V_total = V1 + V2 + V3 + …
- Voltage Divider – V_Rx = V_total × Rx / R_total
Properties
- Ek hi path – agar ek component fail ho to current zero.
- Voltage drop proportional to resistance.
- Power dissipation: P = I²R (same current, different power).
- Used in voltage dividers, Christmas lights (old style).
Parallel Circuit – Formula & Properties
Key Formulas
- 1/R_total = 1/R1 + 1/R2 + 1/R3 + …
- For two resistors: R = (R1×R2)/(R1+R2)
- Equal resistors: R_total = R/n
- V_total = V1 = V2 = V3 = … (same voltage)
- I_total = I1 + I2 + I3 + …
Properties
- Multiple paths – ek branch fail ho to baaki kaam karte rehte hain.
- Current divides inversely proportional to resistance.
- Total resistance hamesha smallest branch se kam hoti hai.
- Used in house wiring (all appliances get same voltage).
Power Calculations (DC aur AC)
Power Formulas
P = V × I (DC / AC resistive, PF=1)
P = I² × R (power loss in resistance)
P = V² / R (power from voltage and resistance)
AC Real Power P = V × I × PF (for AC circuits with PF)
3-Phase Power P = √3 × V_L × I_L × PF × Efficiency
Gulf site pe motor current calculate karte time hamesha Power Factor aur Efficiency dono include karo – warna current kam estimate karoge aur MCB/cable size galat ho sakta hai.
Kirchhoff’s Laws – KVL aur KCL
KCL (Kirchhoff’s Current Law)
- Node pe aane wali current = jaane wali current
- Conservation of charge – sum of currents at a node = 0.
- Used in nodal analysis.
KVL (Kirchhoff’s Voltage Law)
- Closed loop mein voltage drops ka sum = source voltage
- Conservation of energy – sum of voltages around a loop = 0.
- Used in mesh analysis.
Important Theorems (Gulf Interview Level)
| Theorem | What it does | When to use |
|---|---|---|
| Superposition | Multiple sources ko individually solve karke add karo | Linear circuits with multiple independent sources |
| Thevenin’s | Complex network → single voltage source + series resistance | Load pe voltage/current find karna |
| Norton’s | Complex network → single current source + parallel resistance | Alternative to Thevenin |
| Max Power Transfer | RL = RS pe max power | Impedance matching, audio, communication |
Practical Gulf Applications
- Motor Current Calculation: I = P / (√3 × V × PF × Eff). Ye formula Gulf interview mein sabse zyada puchha jaata hai.
- Cable Sizing: Load current ke hisaab se cable size – but derating factors (temperature, grouping) apply karna hota hai.
- DB (Distribution Board) Load: Total connected load ka current nikaal kar incomer MCB rating select karte hain (FLC × 1.25).
- Voltage Drop: V_drop = I × R_cable. Standard limit 3-5% se kam hona chahiye.
- Earthing: Earth resistance < 5Ω – Ohm's law se test current aur voltage drop measure karte hain.
Gulf Interview Tip: Jab koi motor current poochhe – toh Power Factor aur Efficiency dono include karke jawab do. Example: “15kW, 415V, PF=0.85, Eff=0.9 ka current = 27.3A” – ye jawab interviewer ko impress karega.
Gulf Interview – Ohm’s Law Ke Sawaal
- Single phase 230V, 5A load ka power? – P = 230×5 = 1150W.
- 3-Phase 10kW motor ka full load current? – Formula yaad rakhna.
- Series vs Parallel – voltage/current distribution? – Clear difference batao.
- Voltage drop calculation? – I×R ke hisaab se.
- MCB rating selection? – FLC × 1.25.
Ohm’s Law Calculator Use Karo
Voltage, Current, Resistance, Power – ek click me nikaalo. Gulf interview ke liye best practice tool.
VoltGuru.in — Ohm’s Law MCQ — 50 Questions — Free for Gulf Electricians