How can the current be induced in the opposite direction in a transformer?
- Move the magnet out of the coil
- Move the other pole of the magnet into the coil
How can the p.d. be increased?
- Inc. speed of movement of magnet or coil
- Inc. strength of mag. field
- Inc. number of turns on the coil
Why are switch mode transformers used in mobile phone chargers?
- LIGHTER
- More EFFICIENT (less heat)
- SMALLER (portable)
How does regenerative braking work?
HEAT energy lost from braking is converted into ELECTRICAL energy to charge the car’s batteries
What are the benefits of a regenerative braking system?
h
Describe terminal velocity in terms of an object falling through a fluid (3)
- Initial acceleration because of force of gravity
- Gains speed.
- Air resistance increases
- Weight balanced by resist. so resultant force=0
Give two benefits of air bags and seat belts
- Spreads force of impact across upper part of body
- Inc. impact time
What is a benefit of crumple zones and side impact bars?
‘Give way’ to inc. the time taken to change the momentum in a crash, reducing force
What is a thermistors and where would one be used?
A temp sensor for use in fire alarms
What makes a thermistor different to a resistor?
A thermistor’s resistance decreases as temp increases
How could a thermistor be used in a freezer?
Can switch freezer on if temp too high
Can switch off when correct low temp is reached
What do LDRs detect and where could one be found?
Light-dependent resistor
Detects light, could be in auto security lights
What happens to thee resistance of an LDR if the light intensity increases?
THEIR RESISTANCE DECREASES AS LIGHT INTENSITY INCREASES
Describe the functions of these components:
1) Diode (2) Light-emitting diode (3) Variable resistor (4
- Allows d.c.
- LED. Emits light when current passes through
- Allows current to be varied
Name two types of bulbs that are less efficient than low-energy bulbs
Halogen
Filament bulbs
Give an advantage of flywheelbrakes
Can boost speed of overtaking
Ek stored as electrical energy in battery
What is a disadvantage of electric brakes?
Waste (heat) energy
Give two disadvantages of ordinary friction brakes
Can wear away easily
Can overheat
