Electricity- Effects of Electric Current & Electrical Devices
📚 Topic Overview: Electricity – Effects of Electric Current & Electrical Devices
This topic explains how electric current can produce heat and magnetism, and how these effects are used
in everyday devices like CFLs, LEDs, fuses, MCBs, electromagnets and electric bells.
It is important for understanding safety, energy-saving lighting, and basic electric mechanisms.
1. Heating Effect of Current, CFL & LED
Concept / Theory
When electric current passes through a conductor, it produces heat. This is called the
Heating Effect of Electric Current. Electric iron, heater, water geyser and simple filament bulbs
work on this effect. CFL (Compact Fluorescent Lamp) and LED (Light Emitting Diode) are lighting devices
that are designed to use less energy than old filament bulbs.
CFL works through gas discharge inside a tube, while LED uses a semiconductor that
emits light when current flows through it.
Analogy / Examples
- Electric iron becomes hot as current passes through its metal coil.
- ఇస్త్రీ బాక్స్లో లోపలి భాగం వేడెక్కడం — కరెంట్ వల్ల వచ్చే వేడి ప్రభావం.
[Conversions/Formulas]
- More current or more resistance → more heat produced (concept, no exact formula needed at this level).
- LED lamps give more light per unit energy than filament bulbs.
-
.
| English | Telugu |
|---|---|
| Heating effect | వేడి ప్రభావం |
| Emission | వెలువరించడం |
| Discharge | ఉత్సర్జన |
| Energy | శక్తి |
| Device | పరికరం |
A family replaces all filament bulbs with LEDs. For the same brightness,
the electricity bill reduces because LEDs waste less energy as heat.
If the question talks about “saving energy in lighting”, the better choice is LED;
if it mentions “gas discharge lamp”, it is referring to CFL.
2. Fuse & MCB – Protection Devices
Concept / Theory
A fuse is a safety device placed in an electric circuit. It has a thin metal wire
that melts when too much current flows. This breaks the circuit and protects wires and appliances
from overheating and possible fire.
An MCB (Miniature Circuit Breaker) is an automatic switch that turns OFF the circuit
during overload or short circuit. It can be turned ON again after the fault is cleared,
unlike a fuse which must be replaced.
Analogy / Examples
- Fuse works like a safety link that sacrifices itself to save the rest of the circuit.
- ఇంట్లో ఎక్కువ పరికరాలు ఒకేసారి ఆన్ చేయగానే MCB ట్రిప్ అయి ఆఫ్ అవుతుంది — లోడ్ అధికం అన్న సూచన.
[Conversions/Formulas]
- Higher current than the rated value → fuse wire melts, MCB trips.
- MCB rating (in ampere) tells how much current it will allow safely.
-
.
| English | Telugu |
|---|---|
| Breaker | విరామకరం |
| Protection | రక్షణ |
| Overload | లోడ్ అధికం |
| Trip | తక్షణ నిలిపివేత |
In many new houses, fuses are replaced by MCBs. When there is an overload,
the MCB lever goes down. After checking the fault, it can be pushed up again
to restore power safely.
“Once used, must be replaced” → Fuse;
“Can be reset, reusable protection device” → MCB.
3. Magnetic Effect, Electromagnet & Electric Bell
Concept / Theory
When electric current passes through a conductor, a magnetic field is produced around it.
This is called the Magnetic Effect of Electric Current (అయస్కాంత ప్రభావం).
If we wind a coil of wire around a piece of soft iron and pass current, it becomes an
electromagnet (విద్యుత్ అయస్కాంతం).
An electric bell uses a విద్యుత్ అయస్కాంతం to pull a small iron piece attached to a
hammer (సుత్తి). The hammer strikes the bell repeatedly, producing sound as long as
current flows in the circuit.
Analogy / Examples
- A soft iron nail wrapped with wire becomes magnetic only when current flows.
- ఫ్యాక్టరీ గేటు వద్ద ఉన్న ఎలక్ట్రిక్ గంట — బటన్ నొక్కగానే సుత్తి గంటను కొడుతూ శబ్దం చేస్తుంది.
[Conversions/Formulas]
- More turns in the coil or more current → stronger electromagnet.
- Electromagnet strength depends on current and number of turns of the coil.
-
.
| English | Telugu |
|---|---|
| Magnetic effect | అయస్కాంత ప్రభావం |
| Electromagnet | విద్యుత్ అయస్కాంతం |
| Hammer | సుత్తి |
| Energy | శక్తి |
Large cranes in scrap yards use a విద్యుత్ అయస్కాంతం to lift heavy iron blocks.
When current is switched off, the అయస్కాంత ప్రభావం disappears and the metal falls off.
If magnetism stops when current stops → it is a విద్యుత్ అయస్కాంతం (electromagnet),
not a permanent magnet.
Short Memory Formula Sheet
- Heating effect → More current / more resistance → more heat.
- CFL → Gas discharge based lighting device.
- LED → Light emitting semiconductor device (energy-saving).
- Fuse → Melts when current exceeds limit, protects circuit.
- MCB → Miniature Circuit Breaker, trips automatically on overload.
- Magnetic effect → అయస్కాంత ప్రభావం of electric current.
- Electromagnet → విద్యుత్ అయస్కాంతం, magnetism only when current flows.
- Electric bell → Uses విద్యుత్ అయస్కాంతం and సుత్తి to produce sound.