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Figure 1 shows an electric steam iron - AQA - A-Level Physics - Question 1 - 2022 - Paper 2
Question 1
Figure 1 shows an electric steam iron. Water from a reservoir drips onto an electrically-heated metal plate. The water boils and steam escapes through holes in the ... show full transcript
Worked Solution & Example Answer:Figure 1 shows an electric steam iron - AQA - A-Level Physics - Question 1 - 2022 - Paper 2
Step 1
Calculate t.
Answer
To find the time t taken for the metal plate to reach its working temperature, we can use the formula for heat transfer: Where:
- is the heat energy (in Joules),
- is the mass of the metal plate (1.2 kg),
- is the specific heat capacity of the metal (450 J kg⁻¹ K⁻¹), and
- is the change in temperature.
Given that the initial temperature is 20 °C and the final temperature is 125 °C, we find :
Now substituting the values:
Since the power of the heater is 2.1 kW (or 2100 W), we can relate energy and power to time:
ightarrow t = \frac{Q}{P}$$ t = \frac{63000}{2100} \ &t \approx 30 ext{ seconds}.Step 2
Determine whether this claim is true.
Answer
To verify whether the iron can generate steam at a rate of 60 g min⁻¹, we first convert this to kg: 60 g min⁻¹ = 0.06 kg min⁻¹.
Now, using the specific latent heat of vaporization of water, we calculate the energy required to convert 0.06 kg of water into steam:
where
- , and
- . \
Substituting these values:
Next, we determine how much power is available for vaporization. Since the power of the heater is 2100 W, the energy available in one minute is:
Since , the claim is true as the energy supplied is sufficient to produce 60 g of steam per minute.