Heriot-Watt University K17PH Physics: Electric Field Strength and Dipoles

Flashcards covering Electric Field strength, Coulomb's Law, and Electric Dipoles based on university physics lecture notes.

Electric field strength $E$ is defined as the __________ acting per unit positive charge $Q$ placed at a point in the electric field.

force $F$

The standard units for Electric Field strength denoted as $E$ are __________.

$$N C^{-1}$$

According to Coulomb's Law, the force $F$ between two charges is given by the formula $F = \frac{Q_1 Q_2}{\_\_\_\_\_\_\_\_\_\_}$.

4 \text{\pi} \text{\varepsilon}_o r^2

When considering the sign of $E$, the electric field points __________ a negative charge ($-Q$).

towards

For a positive charge ($+Q$), the electric field is positive and points __________ the charge.

away from

The expression for electric field strength derived from Coulomb's Law is $E = \_\_\_\_\_\_\_\_\_\_$.

\frac{Q}{4 \text{\pi} \text{\varepsilon}_o r^2}

In a hydrogen atom, the electric field strength experienced by an electron due to the proton at a separation of $5.29 \times 10^{-11} \text{\,m}$ is __________.

$$5.14 \times 10^{11} \text{\,N C}^{-1}$$

A system of __________ positive charges will have a position $P$ where the net electric field $E = 0$.

two

An electric __________ is a pairing of positive and negative charges of equal magnitude separated by a distance $d$.

dipole

In an electric dipole system, there is no __________ charge.

net

Unlike a system of two positive charges, an electric dipole has no point where __________.

$$E = 0$$

The strength of a dipole is defined by the electric dipole moment $p$, which is calculated using the formula $p = \_\_\_\_\_\_\_\_\_\_$.

$$qd$$

The direction of the electric dipole moment vector points from the __________ charge to the __________ charge.

negative; positive

The units for the electric dipole moment $p$ are $C \text{\,m}$ or __________.

Debye ($D$)

The ionic molecule __________ is an example of an electric dipole when in a high temperature vapour state.

NaCl

The measured value of the dipole moment for $NaCl$ is $3.00 \times 10^{-29} \text{\,C m}$, but the calculated value based on $p = qd$ is __________.

$$3.78 \times 10^{-29} \text{\,C m}$$

On the central axis of a dipole, the electric field at a distance $z$ from the midpoint is given by E = \frac{1}{4 \text{\pi} \text{\varepsilon}_o} \frac{p}{\_\_\_\_\_\_\_\_\_\_}.

$$z^3$$

If a dipole has a moment of magnitude $p = 6.2 \times 10^{-30} \text{\,Cm}$, the electric field at a distance of $1.1 \text{\,nm}$ along the central axis is __________.

$$8.4 \times 10^7 \text{\,N/C}$$