A student uses an electric heater to investigate the efficiency of heating a brass block.
She places the heater in a central hole in the brass block, switches the heater on, and measures the temperature of the block each minute for 20 minutes.
The student wants to calculate the electrical energy supplied to the heater.
Record the readings shown on the meters below.
The student wants to calculate the electrical energy supplied to the heater.
Show that the energy supplied to the heater in 20 minutes is about 65,000 J65,000\text{ J}65,000 J.
The student is told that only 48,000 J48,000\text{ J}48,000 J of energy is actually used to raise the temperature of the brass block by 30 ∘C30\text{ }^\circ\text{C}30 ∘C.
State the equation linking efficiency, useful energy output, and total energy input.
The student is told that only 48,000 J48,000\text{ J}48,000 J of energy is actually used to raise the temperature of the brass block by 30 ∘C30\text{ }^\circ\text{C}30 ∘C.
Calculate the efficiency of heating the brass block. Give your answer to 2 significant figures.
The student is told that only 48,000 J48,000\text{ J}48,000 J of energy is actually used to raise the temperature of the brass block by 30 ∘C30\text{ }^\circ\text{C}30 ∘C.
The efficiency of the heater itself is higher than the efficiency of heating the block. Suggest why.
The student is told that only 48,000 J48,000\text{ J}48,000 J of energy is actually used to raise the temperature of the brass block by 30 ∘C30\text{ }^\circ\text{C}30 ∘C.
State one way in which the student could increase the efficiency of heating the brass block.
The graph shows how the temperature of the block increases from 18 ∘C18\text{ }^\circ\text{C}18 ∘C to 48 ∘C48\text{ }^\circ\text{C}48 ∘C during the 20-minute investigation.
Use ideas about heat transfer to help you explain the shape of the graph in:
section A,
The graph shows how the temperature of the block increases from 18 ∘C18\text{ }^\circ\text{C}18 ∘C to 48 ∘C48\text{ }^\circ\text{C}48 ∘C during the 20-minute investigation.
Use ideas about heat transfer to help you explain the shape of the graph in:
section B,
The graph shows how the temperature of the block increases from 18 ∘C18\text{ }^\circ\text{C}18 ∘C to 48 ∘C48\text{ }^\circ\text{C}48 ∘C during the 20-minute investigation.
Use ideas about heat transfer to help you explain the shape of the graph in:
section C.
