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Edexcel IGCSE Physics > Circuits > Flashcards

Circuits Flashcards

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1
Q

What is the relationship between current, voltage and resistance?

(Symbol and word equation)

A
  • V = IR
  • Voltage(Volts) = Current(Amps) x Resistance(Ohms)
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2
Q

What is the effect on current in a circuit when you change resistance?

A

When resistance goes up, current goes down and vice versa

(I = V/R)

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3
Q

What is the relationship between current, charge and time?

(Symbol and word equation)

A
  • I = Q/T
  • Current(Amps) = Charge(Coulombs)/Time(Seconds)
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4
Q

What is current defined as?

A

The rate of flow of charge

(because of the equation I = Q/T)

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5
Q

What is the relationship between voltage, energy and charge?

(Symbol and word equation)

A
  • V = E/Q
  • Voltage(Volts) = Energy Tranferred(Joules)/Charge(Coulombs)
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6
Q

What is voltage/potential difference defined as?

A
  • Energy transferred per unit charge
  • 1V = 1J/C

(because of the equation V = E/Q)

So it is the amount of energy tranferred by the charge carriers between two points in a cuircuit

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7
Q

In solid metallic conductor, what is current a flow of?

A

Negatively charged electrons

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8
Q

How does current work in a series circuit?

A

It is the same at all points in the circuit

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9
Q

What happens to current in a series circuit when you increase the voltage?

A

Current increases

(Because of I = V/R)

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10
Q

What happens to current in a series circuit when you increase the number of components?

A

Current decreases

Because resistance increases, and when resistance increases, current goes down (I = V/R)

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11
Q

How does current work in a parallel circuit?

A
  • The total amount of current in a circuit (dictated by the amount of voltage supplied by the battery and the total resistance) will split between each branch relative to the resistance of the branch
  • The greater the resistance of that branch, the smaller the current and vice versa (I = V/R)
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12
Q

Why is current conserved at a junction? (The same amount of current flows into it that flows out of it)

A

The charge is conserved (no charge has been lost or gained)

(I = Q/T)

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13
Q

How does voltage work in a series circuit?

A
  • The total voltage supplied by the battery/cell is split between all the components in the circuit, relative to their resistance
  • So a component with higher resistance will have higher voltage (V = IR)
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14
Q

How does voltage work in a parallel circuit?

A

The voltage across each branch will all be exactly the same, and will be equal to the voltage supplied by the cell/battery

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15
Q

What are the advantages of using a series circuit?

A
  • All of the components can be controlled by a single switch
  • It is less complex and fewer wires are required
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16
Q

What are the disadvantages of using a series circuit?

A
  • The components cannot be controlled seperately
  • If one component breaks, they all breaks
17
Q

What are the advantages of using a parallel circuit?

A
  • The components can be individually controlled with their own switches
  • If one component breaks, the rest of the circuit can continue to function
18
Q

What are the disadvantages of using a parallel circuit?

A
  • It is more complicated and more wires are required
  • All components have the same voltage, so it is difficult to control the individual voltages of each component

In summary, certain things are better suited for series circuits and some things are better with parallel
l circuits

19
Q

How does current vary with voltage across a fixed resistor or wire and what would the IV graph look like?

A
  • As voltage increases, current increases, and this relationship is directly proportional
  • The graph would be a straight line increasing linearly and through the origin
20
Q

How does current vary with voltage across a filament bulb and what would the IV graph look like?

A
  • As voltage increases, the current increases but at an increasingly slow rate and it will eventually stop, so it is a non linear relationship
  • This is because as voltage increases in a filament bulb, the temperature increases which increases the resistance, meaning current will not increase as much
  • The graph will be a curve, with current going up fast at the start and then slowing down

Temperature increases resistance because it causes the positive and negative ions in the lattice of the metal in the wire to vibrate more, making it harder for electrons to pass through

21
Q

What is a diode and how does it work?

A
  • A diode is a device which allows current to flow in one direction only
  • It does this by having a very high resistance in the reverse direction, meaning no current can pass through (reverse bias)
22
Q

How does current vary with voltage across a diode and what would the IV graph look like?

A
  • With negative voltages there will be no current as resistance is infinitely high
  • There will be a turn on voltage where current goes sharply up
23
Q

What components do you need to investigate the relationship between current and voltage?

A

Make a series circuit with:

  • An ammeter
  • A voltmeter across the component in question
  • A variable resistor
  • A power source
24
Q

What is an ohmic conductor?

A

A component where voltage and current increase directly proportionally

25
Q

What is an LED?

A

A light emitting diode, meaning it will only emit light if current is flowing through it in one direction

26
Q

How can lamps and LEDS be used to indicate the presence of current in a circuit?

A

Since they both light up when there is current in the circuit, they indicate that there is current in the circuit if they light up

An LED, however, will only light up provided the current is flowing in the right direction

27
Q

How does the resistance of a thermistor vary with temperature?

A

As the temperature increases, the resistance decreases non linearly (the decrease gets progressively slower)

28
Q

How does the resistance of a light dependant resistor vary with light intensity?

A

As light intensity increases, the resistance decreases non linearly (the decrease gets progressively slower)

29
Q

How does resistance vary with length of wire?

A

As the length of the wire increases, the resistance increases directly proportionally

Edexcel IGCSE Physics (19 decks)

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