# A HEATING COIL IS RATED AT 70 W, CALCULATE THE TIME IT WILL TAKE THIS COIL TO HEAT 1.4 KG OF WATER AT 30°C TO 100°C

To calculate the time it will take for a heating coil to heat a given amount of water, we can use the formula:

**Q = mcΔT**

where **Q** is the heat energy transferred, **m** is the mass of the water, **c** is the specific heat capacity of water, and **ΔT** is the change in temperature.

In this case, we have:

** m = 1.4 kg **

**c = 4200 Jkg^(-1)K^(-1) **

**ΔT = (100°C – 30°C) = 70°C**

First, we need to calculate the heat energy required to raise the temperature of the water from 30°C to 100°C:

**Q = mcΔT**

**Q = (1.4 x 4200 x 70)J**

**Q ≈ 411,600 J**

Now, we can calculate the time it will take for the heating coil to transfer this amount of heat energy. The **power (P)** of the heating coil is given as **70 W (watts)**.

The relationship between power, energy, and time is:

**P = ΔE/Δt**

where **P** is power, **ΔE** is change in energy, and **Δt** is change in time.

In this case, we know that **ΔE = Q (heat energy transferred)** and **P = 70 W**. We can rearrange the equation to solve for **Δt**:

**Δt = ΔE/P**

**Δt ≈ 411,600 J / 70 W**

**Δt ≈ 5880 seconds**

Therefore, it will take approximately **5880 seconds** or 98 minutes to heat 1.4 kg of water from 30°C to 100°C using a heating coil rated at 70 W.