Things Got Worng On Multiple Choice Flashcards
When does an object falls the fastest
-closest to bottom
And shortest time
The metal surface of a kettle is hot. What happens to the cool air outside the kettle when it comes into contact with the hot kettle
The densuty of the air decreases nd the air rises
A small object O is placed near a converging lens. The lens forms an image behind it
The object O is closer to the lens than itd priniciple focus
A cell has an electromotiveforce of 1.5 V
The cell converts 1.5J of energy when driving 1 C of charge round a complete circuit
What is the purpose of the commutator in a d.c. electric motor
Reverse the direction of the current in the motor coil every half turn
On a cold day, shiny metal rod feels colder to the touch than a black plastic rod- why?
The metal rod is a better thermal conductor than the plastic rod
A man climbs a ladder- which two quantities can be used to calculate the useful power of the man
- the work done by the man
- the time taken
When does electromagnetic induction occur
Only when a magnet is moved away from a nearby conductor
A steel magnet is placed inside a coil of a wire - how to demagnetise it
Connect the coil to an ac power supply and slowly remove the magnet from the coil
The emf of a rechargeable battery is 6v- what does this mean
6J of energy is provided by the battery to drive a charge of 1 C around a complete circuit
On a cold day, a metal front door knob X and a simmilar plastic knob Y are at the same temp- hy does X feel cooler to the touch than Y
X is a better thermal conductor than Y
When molecules of a gas rebound from a wall of a container, the wall experiences a pressure. What causes this pressure
The change in momentum of the molecules
A force acting on a moving ball causes its motion to change. The force stays constant. What makes the force produce a greater change in the motion of the ball
Decreasing the total mass of the ball
A car is moving in a staight line one a level road. Its engine provides a forward force on the car. A second force of equl size acts on the car due to resistive forces - what happens
The car moves at a constant speed
A student runs up a flight of stairs. What is not needed to know in order to calculate the rate at which the student is doing work against gravity?
The length of the flighof stairs
A child sits on a bouncy hopper and vol decreases. The temp of the air inside it does not change. How does the airpressure in the toy change and why?
- pressure increases
- air molecules strike the rubber more frequently
A strip of iron and brass are attatched to each other making a bimetallic strip. It is heated and the bimetallic striip bends up (withh iron being the top metal). The bimetalic strip is ow cooled and becomes striaght again- what causes this?
-the brass contracts more than t he iron
Why do convection currents occur
When cooled, liquds contract and become more dense
A laser is a source of light with a single frequency. What can it be descibed as
Monochromatic
A positive vcharged rod is held near to but not touching, an uncharged metal sphere. The sphere is briefly now connected to the earth. The rod is removed. What can the charge on the sphere be described as
- charged negatively
- negative charges have moved from earth to the sphere
A train of steel nails and a train of iron nails hang form a strong magnet. The trains are thencarefully removed form the magnet. What happens to the trains
Only the train of iron nails falls apart
How does temp change affect the resistance of the thermistor and the current in the circuit
- temp decreases
- resistance of thermistor increases
- current in circuit decreases
How does the ac graph change when a coil spins in a magnetic field
Both amplitude and frequency increases
What is meant by the half life of radioactive isotope
-the time taken for half of the origiional nuclei to decay
