Unit 5 (EM) Review

What is the minimum resistance value needed for a 9 V battery if you don't want more than 0.001 A current flowing?

• 9 Ω

• 1000 Ω

• 0.009 Ω

• 9000 Ω

Answer explanation

Using Ohm's law, we can calculate the resistance value needed to suppress the current to 0.001 A. If the resistance value is higher than the calculated value, the current will be lower.

How many amperes of current is 4.5 mA?

• 4500 A

• 4.5 A

• 0.0045 A

Answer explanation

The metric prefix "milli" refers to "one-thousandth"

For an LED, a certain amount of __________ is required to turn it on.

In a simple circuit, the resistance is ​____________ proportional to the current.

• directly
• inversely
• not

In a simple circuit, the voltage is ​_____________ proportional to the current.

• directly
• inversely
• not

Draw a circuit diagram of a circuit that has a switch, LED, and a resistor connected in series with a 9V battery.

How much power does a charger output if its output voltage is 10 V with 1 A current?

• 0.1 W

• 1 W

• 10 W

• 100 W

Answer explanation

Electric power is calculated by:

(Power) = (Current) x (Voltage)

If x represents the current and y represents the resistance, what mathematical expression calculates the joule heat from a resistor/light bulb?

An electromagnet does which of the followings?

• Induce current with a magnet

• Turn current into a magnet

• Add resistance to a circuit

• Electrify a magnet

An electromagnet can be made stronger by decreasing the __________ of the coil while keeping everything else the same.