Electricity Flashcards
(20 cards)
What is alternating current
Current that constantly changes direction. It fluctuates between positive and negative potential difference.
What is direct current
Always flows in the same direction, potential difference is always positive or negative
Why is AC used in mains electricity
Its easier to use transformers to change the potential difference of alternating current.
Why is 230V the value of voltage in mains if its constantly changing?
230V is the maximum potential difference. It fluctuates between positive and negative 230V.
Name the brown wire and its role
The live wire. It supplies the 230V alternating potential difference.
Blue wire and its role
Neutral wire. Potential difference of 0V and completes the circuit with the live wire. It carries current away from the device.
Green, yellow striped wire and its role
Earth wire. It has a potential difference of 0V and prevents appliances from becoming live by earthing current.
What happen when an appliance becomes live
The fuse is melted and the huge current flows through the earth wire into the earth.
Why can shocks occur even when the switch is off (open)?
Your body provides a link between the live wire and the earth, current flows through you as there is a large gap in potential difference
Describe the structure of a cable
Made of highly conductive copper and insulated by plastic.
What is electric current
The flow of electrical charge. The size depends on the rate of flow.
What is resistance and give an example
(General def and energy related def)
The opposing force of electrical current. How much energy is needed to drive a current through a component.
For example if 1V is needed to drive 1A through a component it has a low resistance.
How is energy transferred when current flows through a component / wire
Electrons collide with the particles in the conductor which causes a transfer of electrical energy.
This can be turned into other forms of energy such as thermal.
Why does resistance increase with temperature?
At higher temperatures, the particles in the conductor vibrate more so electrons are more likely to collide.
This means there’s more collisions between the particles and electrons so its harder for current to flow, and there’s more resistance.
What are the rules of field diagrams
Lines are at 90 degrees to the surface, and show what happens to a positive object within the field.
What causes electric fields and where are they strongest?
Electrically charged particles have electric fields. They’re stronger closer to the object.
What happens when a strongly charged object interacts with air?
The strong electric field causes the air molecules to lose electrons, ionising the air.
The air can now conduct electricity which is how sparks jump across air.
What is static electricity
The buildup of charge on a material (usually insulating)
How are electrons transferred when creating static electricity
Friction between the objects causes electrons to be transferred to the other object.
Why is it rare for conductors to become statically charged
The electrons flow back to the original materia
