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Physics Paper 1, When drawing cells '+' is on the big side (left…
Physics Paper 1
National Grid
- The National Grid distributes electricity across the country.
- The electricity may be produced by a conventional power station turning a generator or by another method.
- Transformers are used to change voltages stay the same:
- increasing voltage decreases current
- decreasing voltage increases current
- A step-up transformer is used to increase the voltage and reduce the current. Less current means less energy is lost through heating the wire.
- A step-down transformer, reduces the voltage from the transmission voltage to the safer voltage of 230 V for home use.
- Transmission lines: As an electric current flows through the thick cables held up by the pylons, they will get hotter and dissipate energy to the surroundings
- A low resistance and a low current mean that the transmission wires will not heat up as much. As a result, most of the power is delivered to the consumer, and not lost through the wires
Static Electricity
- When insulating materials rub against each other, they may become electrically charged.
- Electrons, are ‘rubbed off’ one material and on to the other.
- The material that gains electrons becomes negatively charged.
- The material that loses electrons is left with a positive charge.
- A polythene rod is rubbed with a duster:
- the polythene rod has gained electrons, giving it a negative charge
- the duster has lost electrons, giving it a positive charge
- An acetate rod is rubbed with the duster:
- the acetate rod has lost electrons, giving it a positive charge
- the duster has gained electrons, giving it a negative charge
- Both the rods and the duster are made of insulating materials. Insulators prevent the electrons from moving and the charge remains static.
- Conductors, on the other hand, cannot hold the charge, as the electrons can move through them.
- If a negatively charged plastic rod is brought near to another negatively charged rod, they will move apart as they repel each other.
- If a positively charged rod is brought close to a negatively charged rod, they will pull together as they attract each other.
Electric Fields
- All charged objects have an electric field around them, which shows how they will interact with other charged particles.
- The closer you get, the stronger the field.
- Electric field shapes:
- An electric field is a region where charges experience a force.
- Fields are usually shown as diagrams with arrows:
- The direction of the arrow shows the way a positive charge will be pushed.
- The closer together the arrows are, the stronger the field and the greater the force experienced by charges in that field.
- This means that the field is stronger closer to the object.
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When drawing cells '+' is on the big side (left side) 230 V, 50 Hz
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Current - flow of electrons, comes from the negative side of the battery, wires have a metallic structure causing it to flow around the wire. Metallic structure - delocalised electrons
Resistance - electrons have to get in between layers, lose a bit of energy each time it hits
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