AC and DC Flashcards

(39 cards)

1
Q

Current definition

A

Rate of flow of charge

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2
Q

What is current measured in

A

Amps

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3
Q

Charge measured in

A

Coulombs

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4
Q

What can result in a high current

A

Lots of electrons moving slowly

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5
Q

What is direct current

A

If the current only flows in one direction

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6
Q

What can supply DC electricity

A

Batteries and cells

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7
Q

What can current do and not do

A

Decrease or increase but not change direction

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8
Q

What is alternating current

A

If the current constantly changes direction and goes negative

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9
Q

What can supply AC electricity

A

Mains electricity

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10
Q

What is energy transferred at in a circuit

A

The speed of light

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11
Q

What is voltage

A

Energy per unit charge

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12
Q

What is potential difference

A

Refers to the energy converted from electrical energy per unit charge

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13
Q

How can we measure current in series

A

Using ammeter

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14
Q

How can we measure voltage in series

A

Voltmeter

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15
Q

What does a series circuit contain

A

All components in a single loop

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16
Q

What is a parallel circuit

A

A circuit containing more that one loop or branch, and may have junctions

17
Q

In a series circuit the current is…

A

The same everywhere

18
Q

In a parallel circuit, the current…

A

Splits at a junction. The current next to the cell is highest

19
Q

Why is the current next to the cell in a parallel circuit the highest

A

All electrons must flow from that wire to the rest of the circuit

20
Q

How can the current in a circuit be increased

A
  • Increasing voltage supplied
  • Decreasing resistance of a circuit
  • Connecting the circuit in parallel (this decreases the resistance)
21
Q

In a parallel circuit the voltage…

A

Is the same for each branch. The voltage across each branch is equal to the voltage across the battery

22
Q

In series the voltage…

A

Along a branch, is shared between the components.

23
Q

What determines the voltage across a component

A

The resistance of the components

24
Q

What causes resistance

A

Electrons colliding with positive ions that form the structure of the metal wire

25
What happens to energy in a resistor
Chemical energy is transferred into thermal
26
What is resistance measured in
Ohms
27
What does a variable resistor do
Change the resistance in a circuit
28
How does a variable resistor change resistance
Increasing or decreasing the length of wire the electricity has to flow through
29
How does a longer length reduce current
The longer the length, the more electrons collide with ions
30
What does ohms law state
Current through a resistor at a constant temperature is directly proportional to the voltage across for a constant resistance Voltage = Current X Resistance
31
What is an LDR
Light dependent resistor
32
What does an LDR do
Change resistance with light intensity
33
What do fixed resistors have
A constant resistance
34
What happens with filament bulbs
They do not obey ohm's law
35
What happens with resistance for an LDR
The higher the light intensity the lower the resistance
36
Where can LDRs be found
Street lamps
37
What does a thermistor do
Change resistance with temperature
38
What happens with resistance in thermistors
The higher the temperature the lower the resistance
39
Where can thermistors be found
Kettles