Paper 1 - Topic 2, Electricty Flashcards by Roger Parry

What is alternating potential difference

A continually oscillating current flow, which results in the potential difference across two points continually oscillating between a positive and negative value

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What is the unit for current

Amps

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What is attraction

A force pulling two opposite charges together when they are brought near each other

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What is the unit for charge

Coulomb

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What is a diode

A component that allows current to flow through in the forward direction and have large resistances in the reverse direction

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What is direct potential difference

A one-directional current flow

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What is the earth wire

A green and yellow striped safety wire that prevents an applicants from becoming live

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What is an electric field

A region in which a charge will experience non-contact, electric force, the field is stronger the closer you are to the charge

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What is an electrical current

The rate of flow of electrical charge, it’s value is the same at any position in a single closed loop

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What is electrical work

When charge flows in a circuit, electrical work is said to be done

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What is a filament lamp

A light emitting component consisting of an enclosed metal filament, it’s resistance increases as the filament’s temperature increases

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What is insulation

The coating around a power cable that prevents electrocution

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What is a light dependent resistor

A light sensitive component whose resistance increases as its temperature decreases

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What is the live wire

A brown wire that carries alternating current from the supply in a mains power supply

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What is mains electricity

An a.c supply, which in the Uk has a frequency of 50Hz and value of 230v

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What is the neutral wire

Blue coloured wire that completes the circuit in a mains power supply

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What is a non-contact force

A force experienced between two separate objects, __eg__ gravity and magnetic and electric forces

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What is an ohmic conductor

A conductor whose current flow is directly proportional to the potential difference across it when held at a constant temperature

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What is the unit for resistance

Ohms

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What does it mean if components are connected in parallel

have the same potential difference across each component
total sum = to the sum of the currents flowing through each component

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What is potential difference

The product of a components resistance and the magnitude of current flow through it

What is repulsion

When two like-charges are brought near each other they repel

What is resistance

A measure of the opposition to current flow

What are step-down transformers

Devices between the transmission cables and the consumer that lower the potential difference of the power so it is at safe, unstable levels

What are step-up transformers

Devices that increase the potential difference generated by a power station, so that the electrical power transmitted along the transmission cables is at higher potential

What is a thermistor

A temperature dependent component whose resistance increases as its temperature decreases

What is the unit for potential difference

Volt

Draw the symbol for an open switch

Draw the symbol for a closed switch

Draw the symbol for a cell

Draw the symbol for a battery

Draw the symbol for a diode

Draw the symbol for a resistor

Draw the symbol for a variable resistor

Draw the symbol for a LED

Draw the symbol for a lamp

Draw the symbol for a fuse

Draw the symbol for a voltmeter

Draw the symbol for an ammeter

Draw the symbol for a thermistor

Draw the symbol for a LDR

What is needed for an electrical charge to flow

- circuit must be closed (no open switches) - there must be a source of potential difference (battery/cell)

How does resistance change with current

- as current increases, electrons (charge) have more energy - when electrons flow through resistor, they will collide with atoms in resistor - this transfers energy to the atoms, causing them to vibrate more - which makes it more difficult for electrons to flow through resistor so as resistance increases, current decreases

How does resistance change with temperature

- in a thermistor: in hotter temps, the resistance is lower and these are often used in temperature detectors/thermostats - in normal wires: when electrons flow through resistor they collide with atoms in resistor, this transfers energy to atoms making them vibrate more

How does resistance change with length

- the greater the length, the more resistance and lower the current - electrons have to make their way through more resistor atoms so it is harder than using a short wire

How does resistance change with light

- LDR: the greater the intensity of light, the lower the resistance, so the resistance is greatest when it is dark, can be used in automatic night lights

How does resistance change with voltage

- Diodes: diodes allow current to flow freely in one direction, in the opposite direction it has a very high resistance so no current can flow

Describe a series circuit

- closed circuit - current only follows a single path - the current is the same everywhere - components are connected end to end - can switch them all off a once - total resistance = the sum of the resistance in each component

Describe a parallel circuit

- branched circuit - current splits into multiple paths - total current in a junction = total current in each of the branches - the potential difference is the same across each branch - components are connected separately to the power supply - current is shared between each of the branches - total resistance is less than the branch with the smallest resistance

What does A.C mean

Alternating current, current continuously varies from positive to negative

What does D.C mean

Direct current, the movement of charge in one direction only, cells and batteries supply direct current

What does power mean

Energy transferred per second, it is directly proportional to current and voltage