GCSE Physics Energy Studies

Practice flashcards covering energy stores, formulas for potential and kinetic energy, specific heat capacity, power, efficiency, and energy resources based on the lecture notes.

What is a system in the context of energy stores?

A system is defined as an object or group of objects.

What energy transfer occurs when a ball hits a wall?

Some of the kinetic energy is transferred as sound.

What energy transfer occurs as a vehicle slows down?

Kinetic energy transfers to thermal energy due to friction between the wheels and the brakes.

What is the formula for calculating kinetic energy ($E_k$)?

$E_k = \frac{1}{2}mv^2$ where $m$ is mass in $kg$ and $v$ is speed in $m/s$.

What is the formula for elastic potential energy ($E_e$)?

$E_e = \frac{1}{2}ke^2$ where $k$ is the spring constant in $N/m$ and $e$ is the extension in $m$.

What is the formula for gravitational potential energy ($E_p$)?

$E_p = mgh$ where $m$ is mass in $kg$, $g$ is gravitational field strength ($9.8\,ms^{-2}$), and $h$ is height in $m$.

How is specific heat capacity defined?

The energy required to raise the temperature of $1\,kg$ of a substance by $1^{\circ}C$ or $1\,K$.

What is the formula for the change in thermal energy ($\Delta E$)?

$E = mc\Delta T$ where $c$ is specific heat capacity in $J\,kg^{-1}{}^{\circ}C^{-1}$ and $\Delta T$ is the temperature change in $^{\circ}C$.

How is power ($P$) defined?

Power is the rate at which energy is transferred or the rate at which work is done.

What are the formulas for power?

$P = \frac{E}{t}$ or $P = \frac{W}{t}$ where $E$ is energy transferred and $W$ is work done.

What power is equivalent to an energy transfer of $1\,joule$ per second?

$$1\,watt$$

According to the transcript, what happens to energy in all system changes?

Energy is dissipated so that it is stored in less useful ways, often described as being 'wasted'.

How does lubrication reduce energy waste in a motor?

It reduces friction so less energy is lost as heat.

How does the thermal conductivity of a material affect the rate of energy transfer?

The higher the thermal conductivity, the higher the rate of energy transfer by conduction across the material.

What conditions result in a low rate of cooling for a building?

The rate of cooling is low if the walls are thick and the thermal conductivity of the walls is low.

What is the formula for efficiency?

$\text{efficiency} = \frac{\text{useful energy output}}{\text{total energy input}}$ or $\frac{\text{useful power output}}{\text{total power input}}$.

What are the two main ways to increase the efficiency of a system?

Reducing waste output (lubrication, insulation) and recycling waste output (e.g., absorbing thermal waste for use as input energy).

What are the main non-renewable energy resources?

Fossil fuels (coal, oil, gas) and nuclear fuel.

What are the main renewable energy resources?

Biofuel, wind, hydro-electricity, geothermal, tidal, solar, and water waves.

Why are non-renewable energy resources often used for large-scale supplies?

Because they have a large energy output per kilogram of fuel.

Why is renewable energy not always considered reliable?

Solar doesn't work at night or in bad weather, and wind is intermittent.