Energy
State the SI unit of energy.
joules
What is a crest of a wave?
Crest is the highest point of a wave.
Give an example of push force.
Any correct ans
Name the meters to measure current and voltage.
Ammeter measures current.
Voltmeter measure voltage.
Give 1 source of portable electrical energy.
battery
State the principle of conservation of energy.
Energy cannot be created or destroyed. Energy can only be transformed from one form to another.
Wave A has higher energy than wave B. Compare the amplitude of each wave.
Wave A has higher energy than wave B. Compare the amplitude of each wave.
What is the formula for Ohm’s law?
V = IR
In a fossil fuel power station, what energy change takes place in the furnace?
Heat energy change to kinetic energy of steam
What energy change takes place when a torch light is turned on for half an hour?
Chemical energy changed to electrical energy, light and heat energy
What is frequency and its SI unit?
Frequency is the number of complete waves produced per second. Its SI unit is hertz.
What are the ways in which a force can do to objects in motion?
Change the speed
Change the direction
Stop the motion
Two resistors of 10 Ω each is connected in series. What is the total resistance?
10 + 10 = 20 Ω
What type of transformer is used when electricity is first transmitted out of power station? Why?
Step-up transformer to reduce the energy loss.
A mountain climber climbed to the top of a mountain. What types of energy does he have at the top of the mountain?
Maximum gravitational potential energy
Kinetic energy is 0
A radio broadcast has a frequency of 93.0 MHz. Convert the frequency to Hz.
93 x 1 000 000 =
93 000 000 Hz
A car travels at a speed of 40 m/s in 5 seconds. What is the distance covered?
200 m
Two resistors are connected in parallel. What would be the effective resistance?
Resistance becomes smaller.
Give 3 examples of fossil fuel.
Give 3 examples of fossil fuel.
Jamie runs up a hill in 10s. If she uses 800 J, calculate the power.
Power = E/t = 800/10 = 80 W
Give 4 uses of radio waves
TV broadcasting
GPS
EZ-link farecard
ERP
A racing car starts from rest to 200 km/h in 10 min. Calculate the acceleration of the car.
Acceleration = 200/ (10/60)
= 1 200 km/h2
Describe how overheating cables takes place.
When too many appliances are plugged into a single socket, a large current will flow out of the socket and may lead to overheating.
Name the device that changes 230 V to 19 V for use in laptop. Explain how does it work.
Device – transformer
IT is a step down transformer that reduces the voltage for use