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Lesson: Ohm’s Law

In this lesson, we will learn how to use the formula V = IR (Ohm's Law) to work out the values of the potential difference, current, and resistance in simple circuits.

Sample Question Videos

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03:47

Worksheet • 20 Questions • 2 Videos

Q1:

A resistor in a circuit has a potential difference of 20 V across it. The current through the resistor is 0.4 mA. What is the resistance of the resistor?

Q2:

A resistor in a circuit has a potential difference of 10 V across it. The current through the resistor is 10 A. What is the resistance of the resistor?

Q3:

The diagram shows a circuit consisting of a cell providing a potential difference of 20 V and a resistor with a resistance of 5 Ω. What is the current through the resistor?

Q4:

What kind of circuit component has a lower resistance if the temperature around the component is higher?

  • AA thermistor
  • BA fuse
  • CAn LED
  • DAn ohmic conductor
  • EA diode

Q5:

A student sets up the circuit shown in the diagram. She uses an ammeter to measure the current through the circuit and gets a value of 2.5 A. She then uses a voltmeter to measure the potential difference across the resistor and gets a value of 10 V. What is the value of the resistance of the resistor?

Q6:

How many millivolts are there in 0.5 volts?

Q7:

Which of the following is the correct unit for potential difference?

  • AVolt
  • BWatt
  • COhm
  • DJoule
  • EAmpere

Q8:

Amir wants to find out the resistance of a resistor. He connects the resistor to a variable potential difference power source and uses an ammeter to find the current through the resistor. His results are shown in the table.

Potential Difference (V) 3 6 9 12 15
Current (mA) 50 100 150 200 250

Q9:

How many volts are there in 20 kilovolts?

Q10:

What is wrong with the circuit shown in the diagram?

  • AAmmeters should not be connected in parallel.
  • BThe current will be different on each side of the resistor; therefore, the ammeter cannot give a reading.
  • CThe signs of the battery are the wrong way around.
  • DAmmeters and voltmeters must always be used together.
  • EThe current is shown as flowing in the wrong direction.

Q11:

What is wrong with the circuit shown in the diagram?

  • AVoltmeters should be connected in parallel across a component.
  • BThe voltmeter will lower the resistance of the circuit.
  • CThe signs of the battery are the wrong way around.
  • DVoltmeters and ammeters must always be used together.
  • EThe current is shown as flowing in the wrong direction.

Q12:

A student has a resistor of unknown resistance. She places the resistor in series with a source of variable potential difference. Using an ammeter, she measures the current through the resistor at different potential differences and plots her results on the graph as shown in the diagram. What is the resistance of the resistor?

Q13:

Ammeters should always be connected in . Voltmeters should always be connected in .

  • Aseries, parallel
  • Bseries, series or parallel
  • Cseries, series
  • Dparallel, series
  • Eparallel, parallel

Q14:

What kind of circuit component has a lower resistance if the light incident upon it is at a higher intensity?

  • AAn LDR
  • BA fuse
  • CAn LED
  • DA diode
  • EA thermistor

Q15:

Which of the following is the correct unit for electrical resistance?

  • AOhm
  • BWatt
  • CVolt
  • DJoule
  • EAmpere

Q16:

The diagram shows three graphs. Each graph shows the current through a component against the potential difference across it.

Which graph shows the characteristics of an ohmic conductor?

  • A(A)
  • B(B)
  • C(C)

Which graph shows the characteristics of a diode?

  • A(A)
  • B(C)
  • C(B)

Q17:

A 2 3 0 0 Ω resistor in a circuit has a current of 100 mA through it. What is the potential difference across the resistor?

Q18:

Which of the following is the correct formula for Ohm’s Law?

  • A 𝑉 = 𝐼 𝑅
  • B 𝑉 = 𝐼 𝑅 2
  • C 𝑉 = 𝐼 + 𝑅
  • D 𝑉 = 𝐼 𝑅
  • E 𝑉 = 𝑅 𝐼

Q19:

A 10 Ω resistor in a circuit has a potential difference of 5 V across it. What is the current through the resistor?

Q20:

A student sets up the circuit shown in the diagram. He sees that the ammeter reads 0.05 A. What value does the voltmeter read?
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