Electricity and Magnetism

Which of the following describes the behavior of a 'hard' magnetic material?

In a magnetic field diagram, what do the arrows on the field lines indicate?

Which property of a material allows it to be magnetized?

What is the name of the effect where a magnetic material loses its magnetism by being hit repeatedly with a hammer?

A solenoid is carrying a current. If an iron core is inserted into the solenoid, what happens to the magnetic field strength?

In the stroking method of magnetization, why must the stroke be repeated many times in the same direction?

Which of the following would produce the most uniform magnetic field?

What is the result of placing two identical bar magnets side-by-side with their like poles together?

Which of the following statements about the Earth's magnetic field is correct?

A bar magnet is falling through a long, vertical copper tube. Compared to falling through a plastic tube, the magnet takes a much longer time to reach the bottom. This is because:

Which property of a wire does NOT affect its resistance?

A resistor has a resistance of $1\text{ k}\Omega$. What is this value in Ohms?

What is the power of a device that uses $100\text{ J}$ of energy in $5\text{ seconds}$?

Which of the following instruments is used to measure potential difference?

Which graph correctly represents the relationship between potential difference ($V$) and current ($I$) for a filament lamp?

The potential difference across a component is $5\,V$ and the current through it is $2\,A$. How much work is done by the electric field in $10$ seconds?

A wire has a resistance of $R$. If it is melted and recast into a wire with half the original length, what happens to the resistance?

A potential divider consists of two resistors of $3.0 k\Omega$ and $6.0 k\Omega$ connected to a $9.0 V$ supply. A voltmeter of resistance $6.0 k\Omega$ is connected across the $6.0 k\Omega$ resistor. What will the voltmeter read?

If the diameter of a wire is reduced by $10\%$ while its length remains the same, by what percentage does its resistance increase approximately?

A thermistor and a fixed resistor are connected in series with a $6 V$ battery. At $20^{\circ}C$, the thermistor resistance is $10 k\Omega$. At $100^{\circ}C$, it is $1 k\Omega$. If the fixed resistor is $2 k\Omega$, what is the change in the output voltage across the fixed resistor?

If the length of a uniform wire is doubled and its cross-sectional area is halved, what happens to its resistance?

A voltmeter is used to measure the potential difference across a resistor. How should it be connected?

A cell has an emf of $6.0\, V$ and an internal resistance of $1.0\, \Omega$. It is connected to a $5.0\, \Omega$ resistor. What is the current in the circuit?

Which statement correctly describes Kirchhoff's First Law?

In the circuit shown, the ideal voltmeter reads $6.0\text{ V}$ when the switch $S$ is open. When the switch $S$ is closed, the voltmeter reading drops to $4.5\text{ V}$. What is the internal resistance $r$ of the battery if the external resistor $R$ has a value of $12.0\, \Omega$?

Two identical lamps are connected in parallel to a battery with negligible internal resistance. If one lamp fails (becomes an open circuit), what happens to the brightness of the other lamp?

A potential divider circuit consists of a $6.0\text{ V}$ battery of negligible internal resistance and two resistors of resistance $P$ and $Q$ connected in series. The output voltage $V_{out}$ is taken across resistor $Q$. If $P = 100\text{ }\Omega$ and $Q = 200\text{ }\Omega$, what is the value of $V_{out}$?

A capacitor-charging circuit in a timing device involves a $12.0 \, V$ D.C. source, a $2.0 \, k\Omega$ resistor, and an initially uncharged capacitor. A discharge path is added via a parallel $3.0 \, k\Omega$ resistor when a switch is toggled. In the steady state of the charging phase (before toggling), what is the potential difference across the $2.0 \, k\Omega$ resistor, and how does the total circuit power consumption change if the $3.0 \, k\Omega$ resistor is then added in parallel to the capacitor?

In a laboratory experiment to determine the resistivity of a new alloy, a student uses a potentiometer of length $L = 1.00 \, m$ and resistance $R_p = 10.0 \, \Omega$. The driver cell has an e.m.f. of $2.00 \, V$ and negligible internal resistance. A test cell with e.m.f. $E_t = 1.50 \, V$ and internal resistance $r = 2.0 \, \Omega$ is connected to the potentiometer. To find the balance point, a shunt resistor $S = 5.0 \, \Omega$ is placed across the test cell. Determine the balance length $x$ on the potentiometer wire.

In a laboratory experiment, three identical lamps are connected to a cell with non-negligible internal resistance $r$. Initially, switch $S$ is open and lamps $L_1$ and $L_2$ are in series. When switch $S$ is closed, lamp $L_3$ is connected in parallel with $L_2$. How do the brightness of lamp $L_1$ and the terminal potential difference of the cell change?

Which safety device uses an electromagnet to quickly open a switch if the current is too high?

What is the result of a fuse 'blowing' in a circuit?

A laptop charger is rated at $90\text{ W}$. How much power is this in kilowatts (kW)?

Which of the following describes alternating current (AC)?

What is the main advantage of an MCB (Miniature Circuit Breaker) over a standard wire fuse?

If the current in an appliance is $5\text{ A}$ and the resistance is $10\text{ \Omega}$, what is the power being used?

In a $230\text{ V}$ AC mains supply, what is the peak voltage approximately?

A 'short circuit' occurs when a low-resistance path is created between the Live and Neutral wires. Why does this frequently cause a fire if no fuse is present?

An electric motor is used to lift a $50\text{ kg}$ mass through a height of $10\text{ m}$ in $5\text{ seconds}$. If the motor operates at $24\text{ V}$ and is $70\%$ efficient, what is the current drawn from the supply?

If a bird stands on a high-voltage ($400\text{ kV}$) power line with both feet on the same wire, why is it not electrocuted?

Which component is found in a microphone to convert sound waves into electrical signals?

What is the direction of magnetic field lines outside a bar magnet?

What is the primary reason for laminating a transformer core?

Which of the following will reverse the direction of the e.m.f. induced in a coil by a moving magnet?

A force $F$ acts on a wire of length $L$ carrying current $I$ in a field $B$. If the current is doubled and the length of the wire in the field is halved, what is the new force?

Which of the following statements about the magnetic field produced by a current-carrying solenoid is TRUE?

An ideal transformer has $N_p = 100$ and $N_s = 400$. The primary is connected to a $12\ V$ DC battery. What is the secondary voltage?

A generator produces an AC voltage given by $V = 311 \sin(100\pi t)$. What is the frequency of the AC supply?

If a magnetic flux through a single loop of wire changes from $0.5 Wb$ to $0.2 Wb$ in $0.05 s$, what is the magnitude of the average induced EMF?

Two very long parallel wires carry currents $I$ and $2I$ in the same direction. At which point is the net magnetic field zero?

Which of the following is a safety precaution when handling radioactive sources?

In a magnetic field, why are alpha particles deflected less than beta particles?

Which of these is a correct pair of an isotope of Hydrogen ($^{1}_{1}H$)?

Which type of radiation can be stopped by a single sheet of paper?

Carbon-14 is an isotope used for radiocarbon dating. If a piece of ancient wood has $25\%$ of the Carbon-14 found in living wood, and the half-life of Carbon-14 is $5700$ years, how old is the wood?

Which particle is identical to a helium-4 nucleus?

Which of the following statements about the nucleus is true?

A Lithium-7 ($^{7}_{3}Li$) nucleus has how many quarks in total? (Hint: 1 proton = 2 up + 1 down; 1 neutron = 1 up + 2 down)

A positron ($\beta^+$) and an electron enter a uniform magnetic field with the same velocity. Which statement is true?

Why is the deflection of a $\beta^-$ particle usually much greater than that of an $\alpha$ particle in the same magnetic field at the same speed?