Electricity Flashcards

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1
Q

What is the definition of current

A

Current is charge flow per unit time (I=Q/t) It is the movement of charged particles which are most commonly electrons

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2
Q

How does current behave in a series circuit

A

Current is constant everywhere in the circuit due to the conservation of charge

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3
Q

What is the unit for charge, current, and potential difference

A

Coulombs, Amperes and Volts

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4
Q

Which way does conventional current flow

A

Conventional current flows from positive to negative however the actual charge from the electrons moves negative to positive

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5
Q

What happens to current in a parallel circuit

A

Current splits at every branch but the sum at any point must be a constant and recombine at some point due to the conservation of charge as current is NOT used up, namely charge isn’t used up

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6
Q

What is the definiton of voltage

A

Potential difference is the difference in electrical potential energy at two points in a circuit, it is defined as the work done per unit charge meaning a volt is defined as a JC^-1. This is because when a charge passes a point, or current flows, through a device, the electrical energy carried by the charged particles often in the form of kinetic energy is converted to other forms of energy such as heat or light, so work is done and a difference in electrical potential energy is created, meaning a voltage

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7
Q

What happens to voltage in a series circuit

A

In series, voltage is used up at each component such that the sum of voltages must equal the total voltage from the supply

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8
Q

What is resistance

A

Resistance is defined as being R=V/I

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9
Q

What is ohms law

A

Ohms law states that V∝I in an ohmic conductor or in other words V=IR where R is the constant of proportionality

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10
Q

Name an Ohmic conductor and two non ohmic conductors

A

A constant resistor and then a filament lamp and a diode

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11
Q

What is the IV graph of a resistor

A

A straight line passing through the origin

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12
Q

What is the IV graph of a filament lamp

A

A curved line flattening further away from the origin and steepening as it gets nearer

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13
Q

What is the IV graph of a diode

A

A straight line up from voltage breakdown up to around 0.7V where the current spikes near vertically as it starts to conduct

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14
Q

What is the purpose of a diode and how can it be protected

A

A diode is a forward-biased conductor which means it only allows current to flow one way and at a certain voltage, say at 0.7V it will start to conduct current freely, anything lower, it won’t conduct and anything higher it may damage it. This can be prevented by adding a resistor into the circuit which will limit the amount of current allowed to flow.

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15
Q

If e, the unit charge or charge on an electron is 1.6x10^-19 C how many electrons are in one coulomb and what consequences does this have?

A

You would so 1\e so around 6.24x10^18 electrons per coulomb as there is 1.6x10^-19 coulombs per electron so the reciprocal would give the value we want

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16
Q

What is Kirchoff’s first Law?

A

Kirchoff’s first Law states that if current splits at a junction then the total current when the junction recombines will be the same as the start, essentially current is constant due to the conservation of charge

17
Q

What is Kirchoff’s second Law?

A

Kirchoff’s second law states that Σε = Σp.d, meaning the sum of the emf is equal to the sum of the p.d

18
Q

What is emf (ε)?

A

EMF is the electromotive force and is defined as the work done for a unit of charge (1C) passing through a cell, ie) ε = W/Q

19
Q

What is a potential divider?

A

A potential divider is where the potential difference is split in proportion to the resistance it is over, meaning a high resistance resistor will get a larger share of the total voltage

20
Q

What is the themistor?

A

A thermistor is a device where it’s resistance decreases when the temperature increases, this is because it is a semi conductor meaning it has very little delocalised electrons and so the added heat delocalises them allowing current to flow. Overall, resistance goes UP when temperature goes DOWN

21
Q

What is an LDR?

A

A light dependant resistor is a device where the resistance goes DOWN as the light level INCREASES