Graduate Medical School Admissions Test (GAMSAT) Section III: Physics Syllabus

Define electric current in terms of charge.

Current is the rate of flow of charge: $I = \frac{Q}{t} = \frac{dQ}{dt}$. SI unit is the ampere (A), $1\,\text{A} = 1\,\text{C\,s^{-1}}$.

Give the formulas for combining resistors in series and in parallel.

Series: $R_{total} = R_{1} + R_{2} + \cdots$. Parallel: $\frac{1}{R_{total}} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \cdots$.

State three equivalent expressions for electrical power dissipated in a resistor.

$P = VI = I^{2}R = \frac{V^{2}}{R}$.

How does the resistance of a wire depend on its dimensions and material?

$R = \frac{\rho L}{A}$, where $\rho$ is resistivity, $L$ is length and $A$ is cross-sectional area. Resistance increases with length and decreases with cross-sectional area.

Give the magnitude of the magnetic force on a current-carrying wire and on a moving charge.

On a wire: $F = BIL\sin\theta$. On a moving charge: $F = qvB\sin\theta$, where $\theta$ is the angle to the field $B$.

State Faraday's law of electromagnetic induction.

The induced EMF equals the negative rate of change of magnetic flux linkage: $\varepsilon = -N\frac{d\Phi}{dt}$, where $\Phi = BA\cos\theta$.

State Lenz's law and explain what the negative sign in Faraday's law represents.

An induced current flows in a direction that opposes the change in flux producing it. The negative sign expresses this opposition, ensuring energy conservation.

Give the transformer equation relating voltages and turns.

$\frac{V_{s}}{V_{p}} = \frac{N_{s}}{N_{p}}$. For an ideal transformer, power is conserved so $V_{p}I_{p} = V_{s}I_{s}$.

Define capacitance and give its formula for a parallel-plate capacitor.

Capacitance $C = \frac{Q}{V}$, in farads (F). For parallel plates, $C = \frac{\varepsilon_{0}\varepsilon_{r}A}{d}$.

Give the formulas for combining capacitors in series and parallel.

Series: $\frac{1}{C_{total}} = \frac{1}{C_{1}} + \frac{1}{C_{2}} + \cdots$. Parallel: $C_{total} = C_{1} + C_{2} + \cdots$ (opposite to resistors).

State the energy stored in a charged capacitor.

$E = \frac{1}{2}CV^{2} = \frac{1}{2}QV = \frac{Q^{2}}{2C}$.

Define wavelength, frequency and wave speed, and give the wave equation.

Wavelength $\lambda$ is the distance between successive identical points; frequency $f$ is cycles per second; the wave equation is $v = f\lambda$.

Distinguish transverse and longitudinal waves with an example of each.

Transverse: oscillations perpendicular to propagation (e.g. light, EM waves). Longitudinal: oscillations parallel to propagation, with compressions and rarefactions (e.g. sound).

State the conditions for constructive and destructive interference in terms of path difference.

Constructive: path difference $= n\lambda$. Destructive: path difference $= \left(n+\frac{1}{2}\right)\lambda$, for integer $n$.

Give the double-slit fringe spacing formula.

$w = \frac{\lambda D}{d}$, where $w$ is fringe spacing, $\lambda$ is wavelength, $D$ is slit-to-screen distance and $d$ is slit separation.

State Snell's law of refraction and define refractive index.

$n_{1}\sin\theta_{1} = n_{2}\sin\theta_{2}$. Refractive index $n = \frac{c}{v}$, the ratio of light's speed in vacuum to its speed in the medium.

What is the critical angle and the condition for total internal reflection?

The critical angle $\theta_{c}$ satisfies $\sin\theta_{c} = \frac{n_{2}}{n_{1}}$ (for $n_{1} > n_{2}$). Total internal reflection occurs when the angle of incidence exceeds $\theta_{c}$.

Give the speed of sound formula's dependence and a typical value in air.

Sound speed increases with medium stiffness and decreases with density; in air at $20^{\circ}\text{C}$ it is about $343\,\text{m\,s^{-1}}$. It is fastest in solids, slower in liquids, slowest in gases.

State the Doppler effect qualitatively for a moving source.

Observed frequency increases as a source approaches (waves compressed, shorter $\lambda$) and decreases as it recedes (waves stretched, longer $\lambda$).

Give the relationship between sound intensity and intensity level in decibels.

$\beta = 10\log_{10}\!\left(\frac{I}{I_{0}}\right)$ dB, where $I_{0} = 10^{-12}\,\text{W\,m^{-2}}$ is the threshold of hearing.

Give the thin lens / mirror equation and define magnification.

$\frac{1}{f} = \frac{1}{u} + \frac{1}{v}$, where $f$ is focal length, $u$ object distance, $v$ image distance. Magnification $m = \frac{v}{u} = \frac{h_{i}}{h_{o}}$.

Contrast converging and diverging lenses by focal length sign and image type.

Converging (convex) lens: positive $f$, can form real or virtual images. Diverging (concave) lens: negative $f$, always forms an upright, diminished, virtual image.

State the first law of thermodynamics.

$\Delta U = Q - W$: the change in internal energy equals heat added to the system minus work done by the system.

Give the equations for sensible heat (temperature change) and latent heat (phase change).

Temperature change: $Q = mc\Delta T$ ($c$ = specific heat capacity). Phase change: $Q = mL$ ($L$ = specific latent heat), with no temperature change during the phase change.

State the ideal gas law and name the variables.

$PV = nRT$, where $P$ is pressure, $V$ volume, $n$ moles, $R \approx 8.31\,\text{J\,mol^{-1}\,K^{-1}}$ the gas constant, and $T$ absolute temperature in kelvin.

Define the components of an atomic nucleus notation $^{A}_{Z}X$ and give the decay particles for alpha and beta-minus decay.

$A$ = mass (nucleon) number, $Z$ = atomic (proton) number. Alpha decay emits $^{4}_{2}\text{He}$; beta-minus decay emits an electron $^{0}_{-1}e$ and an antineutrino (a neutron becomes a proton).

State the radioactive decay law and relate half-life to the decay constant.

$N = N_{0}e^{-\lambda t}$, where $\lambda$ is the decay constant. Half-life $t_{1/2} = \frac{\ln 2}{\lambda}$.

State the photoelectric equation and the meaning of the work function.

$E_{k,max} = hf - \phi$, where $hf$ is photon energy ($h \approx 6.63\times10^{-34}\,\text{J\,s}$) and $\phi$ is the work function, the minimum energy to release an electron from the surface.

Give the de Broglie wavelength formula and mass-energy equivalence.

De Broglie wavelength $\lambda = \frac{h}{p} = \frac{h}{mv}$. Mass-energy equivalence $E = mc^{2}$.

List the seven SI base units and their quantities, and explain the difference between accuracy and precision.

Base units: metre (length), kilogram (mass), second (time), ampere (current), kelvin (temperature), mole (amount), candela (luminous intensity). Accuracy = closeness to the true value; precision = reproducibility/consistency of repeated measurements (small random scatter).