What is a parallel circuit?

A circuit where components are on separate branches, so the current has more than one path.

What is true about p.d. across the branches of a parallel circuit?

It is the same across each branch, equal to the supply p.d.

How do the branch currents in a parallel circuit relate to the supply current?

They add up to the supply current.

How do you find the total resistance of resistors in series?

Add the resistances: R = R₁ + R₂.

How does the total resistance of two resistors in parallel compare with each resistor?

It is smaller than the smallest of the two.

What is the circuit symbol for a cell?

One long line and one short line.

What happens in a series circuit if one lamp breaks?

The circuit is broken, so all the lamps go out.

Why are household lamps wired in parallel?

Each lamp gets the full mains p.d. and works independently of the others.

Series and parallel circuitsIB MYP Sciences: Flashcards

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What is a series circuit?

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What is a series circuit?: A circuit with the components in a single loop, giving only one path for the current.
What is true about current in a series circuit?: It is the same at every point.
How do the p.d.s across components in series relate to the supply p.d.?: They add up to the supply p.d.
What is a parallel circuit?: A circuit where components are on separate branches, so the current has more than one path.
What is true about p.d. across the branches of a parallel circuit?: It is the same across each branch, equal to the supply p.d.
How do the branch currents in a parallel circuit relate to the supply current?: They add up to the supply current.
How do you find the total resistance of resistors in series?: Add the resistances: R = R₁ + R₂.
How does the total resistance of two resistors in parallel compare with each resistor?: It is smaller than the smallest of the two.
What is the circuit symbol for a lamp?: A circle with a cross inside.
What is the circuit symbol for a cell?: One long line and one short line.
What happens in a series circuit if one lamp breaks?: The circuit is broken, so all the lamps go out.
Why are household lamps wired in parallel?: Each lamp gets the full mains p.d. and works independently of the others.
A 12 V supply is across two resistors in series. One has 5.0 V across it. What is the p.d. across the other?: 12 − 5.0 = 7.0 V.

Exam questions on Series and parallel circuits

A student in Mumbai builds a series circuit containing a 9.0 V battery and two lamps, X and Y. An ammeter next to the battery reads 0.30 A, and a voltmeter connected across lamp X reads 3.5 V.
Calculate the resistance of lamp X.2 marks
A student in Lima is drawing a circuit diagram for a model house. Two identical lamps are connected in parallel to a 12 V battery, and a switch controls both lamps. An ammeter in the wire next to the battery reads 1.0 A.
Calculate the current through one of the lamps.2 marks
A technician in Cairo has a 12 V supply, a 4.0 Ω resistor and an 8.0 Ω resistor.
The two resistors are connected in series to the supply. Calculate the current in the circuit and the potential difference across the 8.0 Ω resistor.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).