Other
Electricity
- Course
- Institution
Revision notes for A-Level AQA Physics about topic 5, Electricity
[Show more]
Seller
Follow
maisie2004s
Content preview
ElectricityCurrent
☆ Current is defined as the rate of flow of charge in a circuit.
☆ It is measured in Amperes.
☆ You should be aware of two different ways of describing current
flow:
1. Electron flow is from negative to positive and is the
direction that electrons actually flow in a circuit,
2. Conventional current flow is from positive to negative and
is more commonly used to describe direction.
☆ As an equation, current is defined as:
∆𝑄
I = ∆𝑡
☆ 1 Ampere is the current flow when 1 Coulomb of charge passes a
point each second.
Potential Difference
☆ Potential difference is equal to the work done per coulomb of
charge travelling in a circuit.
☆ As an equation this is defined as:
𝑊
V = 𝑄
☆ It is measured in Volts, where 1 Volt is equal to 1 Joule of work
being done by each Coulomb of charge.
☆ To measure the potential difference over a specific component, a
voltmeter can be used. It should be connected in parallel over
the component.
☆ An ideal voltmeter has infinite resistance, so that no current is
drawn from the circuit.
Resistance
☆ Resistance is a measure of how difficult
it is for current to flow in a circuit.
☆ It is directly proportional to the
potential difference in a circuit, and
inversely proportional to the current
flow.
☆ As an equation it is defined as:
𝑉
R = 𝐼
☆ It is measured in Ohms.
, Electricity
☆ An ohmic conductor is a conductor through which the current flow
is directly proportional to potential difference, when held at a
constant temperature.
Resistivity
☆ The resistance of a material depends on several different
factors.
☆ They are:
1. Cross sectional area
The greater the area, the easier the passage of
electrons,
2. Length
The longer the length, the harder it is to send a
current through it,
3. Resistivity
A property of the material that is assumed under
standard conditions.
☆ Combining these factors allows an equation for resistivity to be
formed:
𝑅𝐴
ρ = 𝐿
☆ The unit for resistivity is Ωm.
Superconductors and Semiconductors
☆ Superconductors are materials which have zero resistivity at and
below a critical temperature.
☆ This temperature differs for each material, but currently are too
low to be usefully used.
☆ If materials with high enough critical temperatures can be
developed, they could be used in electricity transmission to
reduce energy loss as well as in the production of strong
magnetic fields.
☆ Semiconductors are components for which the resistance changes
depending on external conditions.
☆ The two main types you need to know about are:
1. Light Dependent Resistors are light sensitive components -
when light intensity increases, their resistance decreases,
2. Thermistors are temperature sensitive components - when the
temperature increases, their resistance decreases.
Power
☆ Power is defined as the rate of energy transfer.
☆ It can be calculated using:
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller maisie2004s. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.89. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
78252 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now