P3.2 - Flashcards
what is the role of an ammeter?
and where is it positioned in a circuit?
measures current in a circuit
in line with the component - as the current needs to flow THROUGH them
what is the role of a voltmeter?
and where is it positioned in a circuit?
measures the difference in voltage between two points
is positioned on both sides of a component - or on another ‘branch’
in a series circuit, describe the features of:
a) current
b) potential difference
c) resistance
a) current - is equal across all components
b) total pd is equal to addition of all pds
c) res - of all components is different
in a parallel circuit, describe the features of:
a) current
b) potential difference
c) resistance
a) current - split between different branches NOT EQUAL
b) pd across all components are equal
c) res - of all components are different
also: the greater the resistance, the smaller the current going through it. (most electrons want to do easiest things in life, so most electrons go through least resistance)
in a symbol of a cell, which one is positive and which is negative?
long one = positive
short one = negative
what two factors does current depend on?
- resistance
- potential difference
what is the equation to calculate potential difference?(give units and full words)
V = IR
potential difference (V) = current (A) x resistance (Ω)
define potential difference
the difference in voltage between two points
what is the difference between a variable resistor and a normal resistor?
a variable resistor’s resistance can change, a normal resistor’s resistance cannot
how does a battery cause a current to flow in a circuit?
in a cell, the positive terminal is at a higher electric potential than the negative terminal.
and so there is a POTENTIAL DIFFERENCE in which the electrons move from the higher energy terminal to the other (to balance out)
what is the equation to calculate the energy transferred in a circuit?
E = V x Q
energy transferred (J) = potential difference (V) x charge (C)
state the factor which allows the transfer energy in a circuit
resistance
explain how a hotter wire affects the resistance
- in wire/component, ions usually vibrate up and down
- vibrating ions get more energy so they vibrate faster
- so more electrons collide with the ions
SO MORE RESISTANCE AS MORE ENERGY IS TRANSFERRED BY CURRENT
describe current (2)
Current is the rate (1) of flow of charge (1)
describe voltage (1)
Voltage is a measure of the energy carried (1) by the current per coulomb of charge (1)
describe potential difference (2)
Potential difference is a measure of the work done (1) per coulomb of charge (1)
(diff in voltage between two points)
role of variable resistor?
to alter the current
the higher the resistance, the less energy transferred by current as it passes through resistance.
true or false?
false.
The higher the resistance, the more energy transferred by the current as it passes through the resistance.
what is a sensor circuit?
A sensor circuit is a circuit which turns a component on/off automatically, in response to external stimuli.
if confused abt LDR, watch this video:
https://youtu.be/GU1F-EgXFAQ?feature=shared
a) Draw the circuit of a LDR-based street lamp (2)
b) Explain how street lamps work (6).
a)
|———– il————|
| |
| fixed resistor
| |
| |————
| LDR |
| | indicator (lamp)
| | |
|—————————————. (2)
b)
Any 3 from:
- at low light levels, resistance in LDR is higher than at high light levels
- thus a greater proportion of current goes through the lamp than at high light levels
=> since the Lamp resistance: LDR resistance is lower
- this amount of current flowing through the lamp is high enough to switch it on
Any 3 from:
- at high light levels, resistance in LDR is low
- thus a smaller proportion of current goes through the lamp than at low light levels
=> since the Lamp resistance: LDR resistance is higher
- this amount of current flowing through the lamp is not high enough to switch it on
Draw symbol for:
- fixed resistor
- variable resistor
- diode
- LED
- LDR
- thermistor
- indicator
- motor
- ammeter
- open switch
- closed switch
- cell
- battery
- fuse
- heater
- voltmeter
all on 10A physics onenote
what is a battery
two or more cells joined together
what is an indicator
something that indicates that a current works
what is a diode
something that allows a current to only flow in one direction
what is the purpose of a fuse
to stop the current from getting too high (by exploding before that point)
purpose of voltmeter
measure p.d
purpose of ammeter
measures current
as light levels increase, what happens to the resistance of LDR?
resistance decreases
at temp increases, what happens to resistance of thermistor?
resistance decreases
