IB Physics 1, HL
Name:
Period 3 6
Date: Tues., April 28th, 2026
IB PRACTICE PROBLEMS - CIRCUITS
1. This question is about aspects of a filament lamp.
A filament lamp is operating at normal brightness. The potential difference across the lamp is 6.0 V. The
current in the filament is 0.20 A. For the filament of this lamp, calculate
a.
the resistance.
b. the power dissipated.
c.
The lamp in (a) is connected in the circuit shown. The lamp is still operating at normal
brightness. The battery B has an internal resistance of 5.0 Ω and the resistance R of the
resistor is 15 Ω.
i. Calculate the current in the resistor R.
ii. Determine the e.m.f. of the battery.
2. This question is about static electricity and current electricity
In order to investigate the variation of the current I in a variable resistor with the potential difference V
across it, a student set up the following circuit.
Practice problems are ungraded – helpful for next quiz on Thurs., 5.7 (Individual – can be re-assessed) and Group assessment on Wed.,
5.6 (cannot be re-assessed), as well as the Unit Test on May 12th (Tues.)
IB Physics 1, HL
a. Use the graph to deduce that, for the battery,
i.
its emf is 4.5 V.
ii.
its internal resistance is 1.2 Ω .
b. The battery in (a) is to be used as the power source for an electrical device. The device is rated
as 0.8 V, 1.5 A.
Complete the circuit below to show how the battery may be connected so that the device
operates normally. Calculate the value of any other component you may
use.
c.
An electric heater contains a number of similar heating elements, connected as shown to a
supply of V volts. The switches S1 and S2 are shown “open”.
Each heating element dissipates power P when connected to a supply of V volts. The resistance
of each element may be considered to be constant. Complete the table below to give the total
power dissipated, in terms of P, for the switches in the positions indicated.
Practice problems are ungraded – helpful for next quiz on Thurs., 5.7 (Individual – can be re-assessed) and Group assessment on Wed.,
5.6 (cannot be re-assessed)
IB Physics 1, HL
Switch Positions
Total Power
S1 closed, S2 closed
S1 closed, S2 open
S1 open, S2 open
3. A student is set the task of measuring the current-voltage (I-V) characteristics of a filament lamp. The
following equipment and information are available.
Information
Battery
emf = 3.0 V, negligible internal resistance
Filament lamp
marked “3 V, 0.2 A”
Voltmeter
resistance = 30 kΩ, reads values between 0.0 and 3.0 V
Ammeter
resistance = 0.1 Ω, reads values between 0.0 and 0.5 A
Potentiometer
resistance = 100 Ω
a. For the filament lamp operating at normal brightness, calculate
i. its resistance;
ii. its power dissipation.
b. The student sets up the following incorrect circuit.
i. Explain why the lamp will not light.
Practice problems are ungraded – helpful for next quiz on Thurs., 5.7 (Individual – can be re-assessed) and Group assessment on Wed.,
5.6 (cannot be re-assessed)
IB Physics 1, HL
ii. State the approximate reading on the voltmeter. Explain your answer.
c.
On the circuit diagram below, add circuit symbols to show
the correct position of the ammeter and of the voltmeter in
order to measure the I-V characteristics of the lamp.
d. On the axes below draw a sketch graph to show the I-V characteristics for this filament lamp.
e. Explain the shape of the graph that you have
drawn in (d).
4. This question is about electric circuits.
A student sets up the circuit below in order to measure the current-voltage (I-V) characteristic of a small
filament lamp.
a. The supply is a battery that has an emf of 3.0 V and the ammeter and voltmeter are considered
to be ideal. The lamp is labelled by the manufacturer as “3 Volts, 0.6 Watts”.
Practice problems are ungraded – helpful for next quiz on Thurs., 5.7 (Individual – can be re-assessed) and Group assessment on Wed.,
5.6 (cannot be re-assessed)
IB Physics 1, HL
i. Explain what information this labelling provides about the normal operation of the lamp.
ii. Calculate the current in the filament of the lamp when it is operating at normal brightness.
b. The student sets the variable resistor to its maximum value of resistance. She then closes the
switch S and records the following readings.
Ammeter reading = 0.18 A
Voltmeter reading = 0.60 V
She then sets the variable resistor to its zero value of resistance and records the following
readings.
Ammeter reading = 0.20 A
Voltmeter reading = 2.6 V
i. Explain why, by changing the value of the resistance of the variable resistance, the potential
difference across the lamp cannot be reduced to zero or be increased to 3.0 V.
ii. Determine the internal resistance of the battery.
c.
Calculate the resistance of the filament when the reading on the voltmeter is
i. 0.60 V.
ii. 2.6 V.
Practice problems are ungraded – helpful for next quiz on Thurs., 5.7 (Individual – can be re-assessed) and Group assessment on Wed.,
5.6 (cannot be re-assessed)
IB Physics 1, HL
d. Explain why there is a difference between your answers to (c)(i) and (c)(ii).
e. Using the axes below, draw a sketch-graph of the I-V characteristic of the filament of the lamp.
(Note: this is a sketch-graph; you do not need to add any values to the axes.)
Practice problems are ungraded – helpful for next quiz on Thurs., 5.7 (Individual – can be re-assessed) and Group assessment on Wed.,
5.6 (cannot be re-assessed)