Topic 10

Created by

Stylish squirrel 21

Cards (70)

What three subatomic components make
up an atom?
● Electrons
● Protons
● Neutrons
Describe the structure of an atom
● Neutrons and protons in the nucleus
● Electrons surrounding the nucleus in
shells
An atom contains two types of charged
particles, name both of them and state
their charges
● Proton (+1)
● Electron (-1)
In a closed circuit, if there is a potential difference in
the circuit there will also be a ...
Current
How is current defined?
As the rate of flow of charge (or
electrons) around a circuit.
What are the units of charge?
Coulombs, C.
Draw the circuit symbol for a...
Switch, ammeter, diode, resistor, thermistor, varaiable resistor, LDR, LED.
What are the two ways that a component can be
connected in a circuit?
Series (same loop) and parallel (adjacent loop)
Voltage is also known as ….
Potential difference
How does the potential difference across two
components vary when connected in series and
parallel?
In a series circuit the total P.D is
shared between each component
● In a parallel circuit the P.D across each
component is the same
If two resistors are connected in parallel,
what can be said about their combined
total resistance?
Their total resistance is less than the
smallest of the two individual
resistances.
If two resistors are connected in series, what can be
said about their total resistance?
Their total combined resistance is equal
to the sum of the two individual
resistances.
Where must a voltmeter be placed in a circuit?
In parallel with the component that is being
measured.
Give an equation relating potential difference with
energy transferred and charge
Potential difference (V) = energy
transferred (J) / charge (C)
V=E/Q
A volt can also be described as a ...
Joule per coulomb
What is an electric current?
The rate of flow of charge.
State the equation linking charge, current and time.
Give the units for the quantities involved.
Q = I t
Charge (Coulombs), Current (Amperes),
Time (Seconds)
What can be said about the value of
current at any point in a single closed
loop?
Current is the same at all points in a
closed loop.
What two factors does the current in a circuit depend
on?
Potential difference (V) and resistance (R)
What equation should be used to
calculate potential difference if current
and resistance are known? State the
units for all 3 quantities.
V = I R
Potential Difference (V), Current (A),
Resistance (Ω)
What is an ammeter and where must it
be connected in a circuit?
An ammeter measures current. It is
placed in series with the component it is
required to measured.
What happens when current reaches a
junction in a circuit?
Current is conserved; the total current
remains the same and is split between
the two branches.
How does resistance affect current in a circuit?
As the total resistance of a circuit
increases, the current flowing through the
circuit decreases.
How can the current in a circuit be varied?
Using a variable resistor
Give the equation linking current with resistance
p.d. (V) = current (A) x resistance (Ω)
V = IR
How is total resistance affected by two
resistors in series?
The total resistance increases; it is equal
to the sum of the two resistors.
How is total resistance affected by two
resistors in parallel?
The total resistance decreases; it is less
than the resistance of the resistor with
the lowest resistance.
What is an ‘Ohmic Conductor’? State the
condition required
● A conductor for which current and potential
difference are directly proportional
● Resistance remains constant as current
changes
● Temperature must be constant
List four components for which
resistance is not constant as current
changes
Filament lamps, diodes, thermistors and light dependant resistors (LDRs)
What happens to the resistance of a filament lamp
as the temperature increases? Why?
● Resistance increases
● Metal ions have more kinetic energy, so
vibrate more, colliding more frequently with
electrons as they flow through the metal
● This creates more resistance to current flow
What is different about current flow
through a diode?
● The current only flows in one direction
● Resistance is very high in the other
direction, preventing current flow
State what happens to the resistance of a thermistor
as temperature increases.
The thermistor’s resistance decreases.
Give two examples of when a thermistor
may be used.
In a thermostat to turn a heater on
below a certain temperature
In a freezer to turn on a cooler when
the temperature becomes too high
State what happens to the resistance of
an LDR as light intensity decreases.
The LDR’s resistance increases
Give an application for a LDR.
● Street lamps or night lights
● When light levels drop (at night),
resistance increases and the light
gains sufficient current to turn on
How do diodes work?
A diode only allows current to flow in one
direction. If current is flowing the right
way, the resistance is large for small
voltages (up until about 0.6V), but then at
higher voltages becomes very small.
What factors affect the energy transferred when
charge flows through a component?
● Amount of charge
● The potential difference across the
component
Give an equation linking energy, current and p.d.,
giving all SI units
energy (J) = p.d. (V) x current (A) x time (s)
E = VIt
Define potential difference in terms of charge.
The work done per unit charge.
Give an equation relating potential difference to
charge
energy transferred (J) = charge (C) x p.d. (V)
E = QV