Components in Series & Parallel Circuits Flashcards
All 23 cards in this deck
What is true about the current at every point in a series circuit?
It is the same at every point in the circuit.
How is the potential difference of the supply shared in a series circuit?
It is shared between the components; the p.d.s across the components add up to the supply p.d.
How do the branch currents relate to the current from the battery in a parallel circuit?
The currents in the branches add up to the current coming from the battery.
True or false? In a parallel circuit the potential difference across each branch is the same as the supply potential difference.
True. Each branch is connected directly across the supply, so each gets the full p.d.
Why does connecting two resistors in series increase the net resistance?
The current has to pass through both resistors, so the total opposition to the current is greater.
Why does connecting two resistors in parallel decrease the net resistance?
There are more paths for the current, so the total current is greater for the same voltage.
How do you find the total resistance of two resistors connected in series?
Add the resistances: total resistance = .
In the core practical to investigate how current varies with potential difference for a resistor, what is changed and what is measured?
A variable resistor is adjusted to change the p.d. Measure the p.d. across the resistor with a voltmeter in parallel and the current with an ammeter in series.
When testing series circuits, what happens to the brightness of a lamp when a second identical lamp is added in series?
The lamp is dimmer, because the total resistance is greater so the current is less and the p.d. across each lamp is shared.
True or false? Two identical lamps connected in parallel to a supply are brighter than the same two lamps connected in series to that supply.
True. In parallel each lamp has the full supply p.d. across it, so a bigger current flows through each lamp.
What shape is the current–potential difference graph for a fixed resistor at constant temperature, and what does it show about resistance?
A straight line through the origin; the resistance is constant.
What shape is the current–potential difference graph for a filament lamp, and what does it show about resistance?
A curve that gets shallower as the current increases; the resistance increases because the filament gets hotter.
What does the current–potential difference graph for a diode look like?
Almost no current one way (very high resistance), and current rising steeply once the forward p.d. is reached.
How does the resistance of a light-dependent resistor (LDR) vary with light intensity?
The resistance decreases as the light intensity increases (high resistance in the dark).
How does the resistance of an NTC thermistor vary with temperature?
The resistance decreases as the temperature increases.
When investigating how a thermistor's resistance varies with temperature, what is measured at each temperature?
The water temperature (thermometer), the p.d. across the thermistor (voltmeter in parallel) and the current through it (ammeter in series). Resistance = .
When testing a diode in a circuit, what must you do to show that it only lets current flow one way?
Reverse the diode (swap its connections) and take readings again — the current is almost zero in reverse.
In a series circuit, what happens to the other components if one component breaks?
They all stop working, because the only path for the current is broken.
In a parallel circuit, what happens to the other branches if one branch breaks?
They keep working, because each branch is connected to the supply separately.
Why are series circuits often used to test components?
It is easy to change and measure the current and p.d. for the component, and then find its resistance using .
What is the difference between a linear and a non-linear component?
A linear component has a straight-line current–potential difference graph (e.g. a fixed resistor); a non-linear component has a curved one (e.g. a filament lamp).
Give an everyday use of a light-dependent resistor (LDR).
A light sensor, e.g. in street lights or security lights that switch on automatically when it gets dark.
Give an everyday use of a thermistor.
As a temperature sensor, e.g. in a digital thermometer or a fridge's temperature control.