power + efficiency

Question 1

define power.

Answer 1

the rate at which work is performed or energy is transferred, measured in watts

Question 2

power calculation

Answer 2

Question 3

recall the correct equation to calculate
power from work done and time.

Answer 3

Question 4

state the energy transferred in joules per second in watts.

Answer 4

Question 5

give examples to illustrate the definition of power

Answer 5

Electric Kettles (Higher Power = Faster Heating): A 3000 W (3 kW) kettle is more powerful than a 2000 W kettle. This means the 3000 W kettle transfers 3000 Joules of electrical energy to thermal energy per second, allowing it to boil water faster.
Electric Motors (Same Work, Faster Time): Two electric motors lift a 2N weight 10 meters. Motor A does this in 5 seconds, while Motor B takes 10 seconds. Because Motor A transfers the same amount of energy in half the time, it is twice as powerful.
Lightbulbs (Energy Conversion Rate): A 100 W bulb is more powerful than a 60 W bulb because it converts 100 Joules of electrical energy into light and heat per second, compared to 60 Joules for the smaller bulb.

Question 6

efficiency calculation

Answer 6

Question 7

describe ways to increase the efficiency of an intended energy transfer.

Answer 7

efficiency of energy transfer can be increased by reducing wasted energy—often dissipated as heat or sound—thereby ensuring more input energy is converted into useful output. Common methods include lubrication to reduce friction, insulation to prevent heat loss, and upgrading to modern, efficient technology

Question 8

reducing friction to increase the efficiency of an intended energy transfer

Answer 8

Using lubricants or bearings in mechanical systems stops moving parts from rubbing together, preventing kinetic energy from turning into wasted heat.

Question 9

improving insulation to increase the efficiency of an intended energy transfer

Answer 9

Applying insulation materials in homes or around pipes prevents heat loss, ensuring more thermal energy stays within the system.

Question 10

upgrading technologies to increase the efficiency of an intended energy transfer

Answer 10

Replacing old, inefficient devices with modern alternatives, such as using LEDs instead of filament bulbs, which produce less heat and more light.

Question 11

reducing energy waste to increase the efficiency of an intended energy transfer

Answer 11

Tightening loose components reduces vibration and noise, and optimizing processes (e.g., heating only the necessary amount of water) increases efficiency