April 26/28

Physics

Table of Contents#. Date Title-Page – Page Number29.April 14/15 Electrostatics30.April 18/19 Electric Field31.April 20/21 Electrostatics Problems32.April 22/25 Circuits33.April 26/28 Measuring Electricity

1

Homework #4

In:

Label each diagram as series or parallel:

Objective: To understand Ohm’s

law and measure:• Simple• Series• Parallel circuits

Success criteria:

Calculate and measure current, voltage and resistance.

Amount of charge passing by every second:

CurrentI=ΔQ Δt

Measured in Amperes1 Ampere= 1 Coulomb

second

If a current of 45.0 mA exists in a metal wire, how much charge goes through in 20 minutes?

How many electrons flow past a given cross section of the wire in 10.0 min?

Sketch the direction of the current and the direction of the electrons’ motion.

Energy of each charge

Electric potential

V measured in Volts

Energy

charge

• Voltage is like a pinball machine pushing the electrons out of the source into the circuit

Resistance to flow of electrons

Resistance

Measured in Ohms

Ω

• Resistance slows down the flow of electrons– Voltage used up – Light emitted– Heat emitted

• How do you think the current would change if you increase the resistance in a circuit?

• How do you think the current would change in a circuit if you increase the voltage into a circuit?

Ohm’s Law

Georg Simon Ohm

• German physicist

• The relationship between current and voltage

• 1827

Ohm’s Law

V=IR

A lightbulb has a resistance of 240 Ω when operating at a voltage of 120 V. What is the current in the bulb?

A toaster has a resistance of 10 kΩ. How much current flows through it at a voltage of 120V?

What is the resistance of a hair dryer if it runs at 120V with a current of 1 A?

What is the current of a lightning bolt that has a voltage of 10 million volts through air with a resistance of 2 KΩ?

Lab: Using a Multimeter

Purpose: to measure circuits.

How to measure resistance voltage and current

Reading a Resistor

Measuring Voltage

• -Direct measurement of the push

• -Connect directly to the battery (or circuit if you want to measure change in voltage)

Measuring Resistance

-Connect leads to resistor

-Outside of a circuit

Measuring Current

• Must be a circuit

• Circuit must include the meter

Out:

A hairdryer takes 1 amp of current at 120 V. What is its resistance?