Class notes
current electricity digital notes
- Course
- PHY103 (PHY103)
- Institution
- University Of Manitoba (UManitoba )
Current and electricity notes provide in-depth knowledge
[Show more]
Seller
Follow
Content preview
CHAPTER # 13CURRENT ELECTRICITY
Q1: Define Current.
CURRENT
“Amount of charge passes through a conductor per unit time is called current”.
OR
“Flow of charge per unit time in a conductor is known as “current”
Formula:
If “Q” coulomb charge passes through a wire in time “t” seconds, then current “I” can be
defined by the following formula as:
𝑸
𝑰=
𝒕
Unit:
S.I unit of current is ampere (A) which is equal to coulomb/sec.
Direction of current:
There are two direction of current:
1- Electronic current
2- Conventional current
1- Electronic current:
The direction of flow of negative charges (electrons) through a
conductor is referred as “Electronic current”.
This current is always taken from negative to positive terminal
of battery.
2- Conventional current:
The direction in which positive charges move in a circuit is
referred as “Conventional current”.
This current is always taken from positive to negative terminal
of battery.
We always consider the direction of conventional
current while studying.
Q2: Why does current is not measured without applying potential difference across the
conductor while charges (electron) move within the conductor with thermal speed?
ANSWER:
There is large number of free electrons present in a conductor which move with thermal
speed (speed due to thermal energy) in all directions of a conductor so that the net
movement of charges or electrons in a particular direction is zero, that’s why current is not
measured in this situation.
, Q3: Define drift speed or drift velocity.
DRIFT VELOCITY
“The velocity of electrons within the conductor when potential difference or external
electric field is applied across the end of the conductor is known as drift velocity”.
Explanation:
When potential difference or external electric field is applied across the end of a conductor,
the electrons are accelerated from negative to positive ends of a conductor. These electrons
collide with the atoms during their motion, so that kind of velocity is referred as
drift velocity. It is the order of 0.01 m/s.
Expression for drift velocity: (Optional)
Consider a conductor of length “l” and of cross sectional area “A” which is connected to the
terminal of battery as shown in the diagram. According to definition of current,
𝑸
𝑰=
𝒕
If “N” electrons pass through the conductor in time “t” then:
𝑵𝒆
𝑰= − − − − − (𝟏) ∵ {𝑸 = 𝑵𝒆}
𝒕
Here we define number of electrons per unit volume which is also called number density (n)
as:
𝑵 𝒏𝒐. 𝒐𝒇 𝒆𝒍𝒆𝒄𝒕𝒓𝒐𝒏𝒔
𝒏= =
𝑨𝒍 𝒗𝒐𝒍𝒖𝒎𝒆 𝒐𝒇 𝒄𝒐𝒏𝒅𝒖𝒄𝒕𝒐𝒓
Here “Al” represents the volume of conductor.
𝒏𝑨𝒍=𝑵
Now equation (1) may be written as:
𝒏𝑨𝒍𝒆
𝑰=
𝒕
𝒍
𝑰 = 𝒏 𝑨( )𝒆
𝒕
𝑺 𝒍
𝑰 = 𝒏 𝑨 𝒗𝒅 𝒆 ∵ {𝒗 = , 𝒗𝒅 = }
𝒕 𝒕
𝑰
𝒗𝒅 =
𝒏𝑨𝒆
Q4: state and explain Ohm’s law. [1995, 2000, 02 PM, 03 PM, 04, 06, 07, 14, 18]
OHM’S LAW
Statement:
“At the same physical state of a conductor the current passes through a conductor (I) is
directly proportional to the potential difference (V) applied across it”.
Mathematically:
𝑰∝𝑽
𝑰 = 𝑲𝑽 − − − − − (𝟏)
Here, “K” is constant called conductance of conductor.
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 zaeeem. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for CA$11.13. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
76449 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now