## • Which bulb will glow brighter?

**When a 60 W, 200 V bulb is connected in series with 100 W, 200 V bulb across a 200 V A.C. power supply, which bulb will glow brighter?**

**Solution:** 60 Watt bulb will **glow brighter** then 100 Watt bulb.

**Why ?**

When two bulb are connected in series across a power supply, the voltage drop across each bulb depends upon its resistance value.

60 Watt power value is less than 100 Watt. Which means 60 watt bulb must have higher resistance value to resist the current flow.

Let us consider,

Resistance of 60 watt bulb = R1

Resistance of 100 watt bulb = R2

Therefore, **R1 > R2**

We know that,

Voltage drop, V = IR

As R1 is greater than R2, therefore voltage drop across 60 watt bulb is more than 100 watt bulb. Hence 60W bulb will consume more power and glow brighter.

**In Short****, the voltage drop across 60W bulb is more than 100W because 60W bulb has higher resistance. Hence 60W bulb will glow brighter.**

## • Find the total energy consumed (in joules) by bulb when it is ON for 6 hours?

When a 100 watt, 220 V bulb is connected across 220 V power supply. Find the total energy consumed by bulb when it is ON for 6 hours?

When a 100 watt, 220 V bulb is connected across 220 V power supply. Find the total energy consumed by bulb when it is ON for 6 hours?

**Solution:** Given that

Power Rating (P) = 100 W

Supply Voltage (V) = 220 V

Energy consumed in 6 hours = ?

**Formula used: **

Energy = Power x Time

Joule = Watt x Second

Convert 6 hours in seconds,

6 hours = 6 x 60 minutes x 60 second

6 hours = 21600 seconds

Now apply formula,

**Energy = Power x Time**

E = 100 x 21600

E = 2160000 joules

E = 2.16 x 106 Joules

Energy consume in kWh,

Energy = Power x Time

E = (100/1000) x 6

E = 0.6 kWh

**In short, When a 100 watt, 220 V bulb is connected across 220 V power supply. It will consume 2.16 x 106 Joules of energy in six hours. **

## • What are the differences between fuse and circuit breaker?

**Fuse**

**1. **It is generally used in low voltage application.

**2. **It can detect and interrupt the fault.

**3. **Its work on the principle of electrical and thermal properties.

**4.** Operating time of fuse is very small.

**5. **Fuse element needs to replace after every operation.

**6. **Fuse cannot be used as an ON/OFF switch.

**Circuit Breaker**

**1.** Circuit breaker is suitable for high voltage application.

**2.** Circuit breaker cannot detect fault. It perform only interruptions and deductions of fault is made by relay.

**3. **Circuit breaker work on the electromagnetical principle.

**4. **Operating time of circuit breaker is higher as compared to fuse.

**5.** Circuit breaker can be used again and again after operation.

**6. **Circuit breaker can be used as an ON/OFF switch.