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Mindmap von Kieran Lancaster, aktualisiert more than 1 year ago
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Erstellt von Kieran Lancaster
vor mehr als 6 Jahre
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CHP 9 - Energy, Power and Resistance Pt1
- Circuit symbols
- A battery is two or more cells put together.
The longer end represents the positive
terminal, the short represents negative
- A battery is two or more cells put together.
The longer end represents the positive
terminal, the short represents negative
- P.d and E.M.F
- One Volt is the p.d across a component when 1J of
energy is transferred per unit charge
- 1V=1JC^-1
- P.d is work done by the charge carriers per unit of charge. The difference in
energy before and after a point. Electrical energy transferred into other forms.
- 1V=1JC^-1
- E.m.f is work done on the charge carriers per unit charge, by
a cell or battery. The charge carriers gain electrical energy
- The formula is
the same as the
one above
- The formula is
the same as the
one above
- One Volt is the p.d across a component when 1J of
energy is transferred per unit charge
- The electron gun
- A small metal filament is heated until some elctrons get
enough kinetic energy to escape the surface of the metal,
in a process called thermionic emission.
- This is placed in a vacuum, with a high, accelerating
p.d between the cathode and anode
- The freed electrons are accelerated towards the anode, gaining
- If there is a small hole in the anode, a fine beam of electrons is created.
- If there is a small hole in the anode, a fine beam of electrons is created.
- The freed electrons are accelerated towards the anode, gaining
- This is placed in a vacuum, with a high, accelerating
p.d between the cathode and anode
- As electrons accelerate, they gain kinetic energy.
P.d=eV, V being the accelerating p.d.
- Work done on electron = gain in kinetic energy
- eV=1/2mv^2
- eV=1/2mv^2
- Work done on electron = gain in kinetic energy
- A small metal filament is heated until some elctrons get
enough kinetic energy to escape the surface of the metal,
in a process called thermionic emission.
- Resistance
- Resistance is the ratio of p.d
Across a component/current
in a component
- The unit is the ohm, were 1Ω=1VA⁻¹
- The unit is the ohm, were 1Ω=1VA⁻¹
- Ohms law states: For a conductor kept at a
constant temperature, current in the wire is
proportional to the p.d across it
- When a wire gets hotter, resistance increases and therefore current
decreases. This is because positive ions vibrate with a greater
amplitude, increasing the frequency of the collisions. The electrons
transfer more energy, which is given off as heat.
- When a wire gets hotter, resistance increases and therefore current
decreases. This is because positive ions vibrate with a greater
amplitude, increasing the frequency of the collisions. The electrons
transfer more energy, which is given off as heat.
- Resistance is the ratio of p.d
Across a component/current
in a component
- I-V characteristics
- The circuit shown left is used to
collect data for an I/V graph, but the
fixed resistor can be any component
- A filament lamp is non ohmic, since p/d
isnt proportional to Current. The
resistance of the lamp is also not constant
- Resistance increases as the p.d across it increases, since
the wire increases with temperature until it glows.
- Resistance increases as the p.d across it increases, since
the wire increases with temperature until it glows.
- A filament lamp is non ohmic, since p/d
isnt proportional to Current. The
resistance of the lamp is also not constant
- Fixed resistors have constant resistance, regardless
of temperature. Voltage is proportional to
temperature, therefore they follow ohms law
- Shallower line = higher resistance, since
R=Inverse of gradient (R=V/I, not I/V)
- Shallower line = higher resistance, since
R=Inverse of gradient (R=V/I, not I/V)
- The circuit shown left is used to
collect data for an I/V graph, but the
fixed resistor can be any component
- Diodes
- A diode only allows current to flow in one particular
direction (shown by the way the 'arrow' faces)
- Some diodes are light emitting diodes, shown
by two arrows. They function the same way as
normal diodes, but light up when current flows
- A diode is non ohmic, and it's behaviour depends on the polarity
- A diode is non ohmic, and it's behaviour depends on the polarity
- Some diodes are light emitting diodes, shown
by two arrows. They function the same way as
normal diodes, but light up when current flows
- The I/V graph for a diode is shown left. When p.d
is negative, resistance is almost infinite. No
current can flow the wrong way through a diode
- When positive, current doesn't flow initially. A
threshold p.d has to be reached (this is the point
and L.E.D starts emitting light, the threshold p.d
determines the colour/frequency of light)
- From this point, for every small increase in p.d,
resistance drops sharply.
- From this point, for every small increase in p.d,
resistance drops sharply.
- When positive, current doesn't flow initially. A
threshold p.d has to be reached (this is the point
and L.E.D starts emitting light, the threshold p.d
determines the colour/frequency of light)
- A diode only allows current to flow in one particular
direction (shown by the way the 'arrow' faces)
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