# Worksheet: Ohm’s Law and Calculation of Resistance

In this worksheet, we will practice using the formula V = IR (Ohm’s law) to calculate the resistance in simple electronic circuits.

Q1:

A resistor is placed in a circuit with an adjustable voltage source. Measurements of the voltage across and the current through the resistor are shown in the accompanying graph. Find the resistance of the resistor. Q2:

A resistor of resistance 1.8 kΩ is connected across a battery of emf 5.0 V. What is the current through the resistor?

Q3:

Calculate the effective resistance of a pocket calculator that has a 1.35 V battery if the current through the calculator is 0.200 mA.

Q4:

What is the voltage supplied to a short circuit of power 1.44 kW through a 0.100 Ω resistance?

Q5:

Currents of 0.06 A can potentially kill people by making their heart fibrillate (beat in an uncontrolled manner).

What voltage can produce 0.2 A of current through a dry human body with an average resistance of 100 kΩ?

A human body is made wet by heavy rain. The body has an average resistance of 100 Ω. What voltage can induce fibrillation in these circumstances?

Q6:

A resistor is connected in series with a power supply of 35 V, producing a current in the resistor of 0.25 A. What is the resistance of the resistor?

Q7:

An indicator light on a DVD player has a resistance of 300 Ω and the current in the light is 55.0 mA. How many volts are supplied to operate the light?

Q8:

What is the current through the bulb of a flashlight that has a resistance of 5.0 Ω if the flashlight is powered by a battery with an emf of 4.5 V?

Q9:

A 58.0 V battery is connected across a resistor combination consisting of a 14.0 Ω resistor and a 46.0 Ω resistor.

Find the current in the 14.0 Ω resistor when the resistors are connected in series.

Find the current in the 46.0 Ω resistor when the resistors are connected in series.

Find the power dissipated by the 14.0 Ω resistor when the resistors are connected in series.

Find the power dissipated by the 46.0 Ω resistor when the resistors are connected in series.

Find the current in the 14.0 Ω resistor when the resistors are connected in parallel.

Find the current in the 46.0 Ω resistor when the resistors are connected in parallel.

Find the power dissipated by the 14.0 Ω resistor when the resistors are connected in parallel.

Find the power dissipated by the 46.0 Ω resistor when the resistors are connected in parallel.

Q10:

A man tries to pick up a burning piece of bread from a toaster with a metal butter knife and comes into contact with 110 V alternating current. He does not even feel it since, luckily, he is wearing rubber-soled shoes. What is the minimum resistance of the path the current follows through the person if the threshold of sensation of the current in the body is 1.00 mA?