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1. GENERAL PHYSICS 2
Science, Technology, Engineering, and Mathematics
WEEK 5
ELECTRIC CURRENT AND CIRCUITS

2. Learning Objectives:
• At the end of this presentation, students will be able to:
1. Describe the relationship between the electrical current,
voltage, and resistance in a circuit.
2. Apply ohm’s law to circuits containing resistance and EMF
3. Illustrate the relationship of resistivity and temperature.
4. Define electromotive force and Electrical power.

3. LETS RECALL!
In chapters 1 and 2, we considered electric forces, fields, and energy in
different situations involving static arrangement of electrical charge.
There are several rate quantities in physics. For instance,
velocity is a rate quantity - the rate at which an object changes its position.
Acceleration is a rate quantity - the rate at which an object changes its velocity.
power is a rate quantity - the rate at which work is done on an object.
Mathematically, power is the work per time ratio.
In every case of a rate quantity, the mathematical equation involves some
quantity over time.

4. When charge move from one place to
another, we can say that there is an
electric current. Electrons can move freely
through a metal.
If the two requirement of an electric
circuit are met, then charge will flow
through the external circuit. It is said that
there is a current - a flow of charge.

6. current - charge is moving.
As a physical quantity, current is the rate at
which charge flows past a point on a circuit. As
depicted in the diagram, the current in a circuit
can be determined of the quantity of
charge Q passing through a cross section of a
wire in a time t can be measured. The current is
simply the ratio of the quantity of charge and
time.

7. current is a rate quantity. Current as a rate
quantity would be expressed mathematically as
𝐼 =
∆𝑄
∆𝑡
Current is measured in units of charge divided
by time, or Coulomb per second (C/s). This unit
has given the name Ampere (A). In honor to
Andre-Marie Ampere for her role in discovering
the Laws of Magnetism.

9. I = ____ A
I = ____ A

11. Which way does the charge move?
Current is defined in terms of net positive
charge flow. Even though electrons are
responsible for the current in metal.
Since electrons are negatively charged, the
electrons in the circuit would be attracted to
the positive terminal of the cell and repelled by
the negative terminal of the cell. So, the
electrons would move away from the negative
terminal and towards the positive terminal.