Two bulbs on the mains
"Two bulbs on the mains" is a free, interactive Class 12 Physics simulation for NEET and JEE, built on the NCERT section "Electrical energy and power" in Current Electricity. Two bulbs of chosen ratings on 220 V wired in series or parallel, glowing by the power each actually takes, with each bulb's voltage share. NEET has asked about this idea 7 times in 10 years of papers. JEE Main asked 65 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Electrical energy and power in Current Electricity. Change the values and watch what happens.
What it shows
NCERT § Electrical Energy, Power
Two bulbs of chosen ratings on 220 V wired in series or parallel, glowing by the power each actually takes, with each bulb's voltage share.
Controls
3 to try
- Sliderbulb A rating 25–200 W
- Sliderbulb B rating 25–200 W
- Segmentedseries / parallel
Try this
Wire a 25 W and a 100 W bulb so the 25 W one glows brighter and read its power (16 W vs 4 W)
Common mistake
Assuming a 100 W bulb always glows brighter than a 25 W bulb.
In NEET
10 years of papers
Asked 7 times in 10 years of NEET.
See the past questions: Ohm's Law and Resistance, Current Electricity (chapter)
In JEE Main
42 shifts analysed
65 questions from Current Electricity across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "Electrical Energy, Power"
- When charge moves through a potential difference V, the energy transferred per unit time is P = VI.
- For a resistor, the power dissipated as heat is P = I²R = V²/R (Joule heating).
- Two appliances rated for the same voltage: the one with the higher power rating has the lower resistance, since R = V²/P.
- In series, the same current flows, so the higher-resistance device dissipates more power; a lower-rated bulb glows brighter when connected in series with a higher-rated one.
- In parallel, the same voltage is applied, so the lower-resistance device dissipates more power.
- Power is sent over long distances at high voltage: for a fixed power P delivered through cables of resistance R_c, the loss P²R_c/V² falls sharply as V is raised.
- The kilowatt hour is the commercial unit of electrical energy, 1 kWh = 3.6 × 10⁶ J.
Questions
5 answers
- What does the "Two bulbs on the mains" simulation show?
- Two bulbs of chosen ratings on 220 V wired in series or parallel, glowing by the power each actually takes, with each bulb's voltage share.
- What mistake does the "Two bulbs on the mains" simulation fix?
- A common mistake it clears up: assuming a 100 W bulb always glows brighter than a 25 W bulb.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 7 times in 10 years of papers.
- Does JEE Main ask questions from Current Electricity?
- Yes. JEE Main asked 65 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Electrical energy and power" in Current Electricity (Class 12 Physics).
Embed this simulation
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